Magento 2.1.1 Invalid block type exception - class not found
<p>Trying to load a custom module's edit/create form.</p>

<p>In my <strong>Magento 2.1.1</strong> on my production system (linux) I get a invalid block type exception caused by class not found while on my local host xampp / windows all works fine.
It occurs when I want to open the form to create or edit a custom entity while the grid works fine.</p>

<pre><code>2 exception(s):
Exception #0 (Magento\Framework\Exception\LocalizedException): Invalid block type: Brainworx\Medipimsync\Block\Adminhtml\Sync\Edit\Form
Exception #1 (ReflectionException): Class Brainworx\Medipimsync\Block\Adminhtml\Sync\Edit\Form does not exist

Exception #0 (Magento\Framework\Exception\LocalizedException): Invalid block type: Brainworx\Medipimsync\Block\Adminhtml\Sync\Edit\Form
#0 /data/sites/web/apovitabe/www/vendor/magento/framework/View/Layout/Generator/Block.php(237): Magento\Framework\View\Layout\Generator\Block-&gt;getBlockInstance('Brainworx\\Medip...', Array)
#1 /data/sites/web/apovitabe/www/vendor/magento/framework/View/Layout.php(760): Magento\Framework\View\Layout\Generator\Block-&gt;createBlock('Brainworx\\Medip...', 'medipimsync_syn...', Array)
#2 /data/sites/web/apovitabe/www/vendor/magento/framework/View/Layout.php(743): Magento\Framework\View\Layout-&gt;_createBlock('Brainworx\\Medip...', 'medipimsync_syn...', Array)
#3 /data/sites/web/apovitabe/www/var/generation/Magento/Framework/View/Layout/Interceptor.php(349): Magento\Framework\View\Layout-&gt;createBlock('Brainworx\\Medip...', 'medipimsync_syn...', Array)
#4 /data/sites/web/apovitabe/www/vendor/magento/framework/View/Element/AbstractBlock.php(382): Magento\Framework\View\Layout\Interceptor-&gt;createBlock('Brainworx\\Medip...', 'medipimsync_syn...', Array)
#5 /data/sites/web/apovitabe/www/vendor/magento/module-backend/Block/Widget/Form/Container.php(108): Magento\Framework\View\Element\AbstractBlock-&gt;addChild('form', 'Brainworx\\Medip...')
#6 /data/sites/web/apovitabe/www/vendor/magento/framework/View/Element/AbstractBlock.php(264): Magento\Backend\Block\Widget\Form\Container-&gt;_prepareLayout()
#7 /data/sites/web/apovitabe/www/vendor/magento/framework/View/Layout/Generator/Block.php(139): Magento\Framework\View\Element\AbstractBlock-&gt;setLayout(Object(Magento\Framework\View\Layout\Interceptor))
#8 /data/sites/web/apovitabe/www/vendor/magento/framework/View/Layout/GeneratorPool.php(86): Magento\Framework\View\Layout\Generator\Block-&gt;process(Object(Magento\Framework\View\Layout\Reader\Context), Object(Magento\Framework\View\Layout\Generator\Context))
#9 /data/sites/web/apovitabe/www/vendor/magento/framework/View/Layout.php(327): Magento\Framework\View\Layout\GeneratorPool-&gt;process(Object(Magento\Framework\View\Layout\Reader\Context), Object(Magento\Framework\View\Layout\Generator\Context))
#10 /data/sites/web/apovitabe/www/var/generation/Magento/Framework/View/Layout/Interceptor.php(89): Magento\Framework\View\Layout-&gt;generateElements()
#11 /data/sites/web/apovitabe/www/vendor/magento/framework/View/Layout/Builder.php(129): Magento\Framework\View\Layout\Interceptor-&gt;generateElements()
#12 /data/sites/web/apovitabe/www/vendor/magento/framework/View/Page/Builder.php(55): Magento\Framework\View\Layout\Builder-&gt;generateLayoutBlocks()
#13 /data/sites/web/apovitabe/www/vendor/magento/framework/View/Layout/Builder.php(65): Magento\Framework\View\Page\Builder-&gt;generateLayoutBlocks()
#14 /data/sites/web/apovitabe/www/vendor/magento/framework/View/Layout.php(244): Magento\Framework\View\Layout\Builder-&gt;build()
#15 /data/sites/web/apovitabe/www/vendor/magento/framework/View/Layout.php(859): Magento\Framework\View\Layout-&gt;build()
#16 /data/sites/web/apovitabe/www/var/generation/Magento/Framework/View/Layout/Interceptor.php(414): Magento\Framework\View\Layout-&gt;getBlock('menu')
#17 /data/sites/web/apovitabe/www/vendor/magento/module-backend/Model/View/Result/Page.php(59): Magento\Framework\View\Layout\Interceptor-&gt;getBlock('menu')
#18 /data/sites/web/apovitabe/www/var/generation/Magento/Backend/Model/View/Result/Page/Interceptor.php(24): Magento\Backend\Model\View\Result\Page-&gt;setActiveMenu('Brainworx_Medip...')
#19 /data/sites/web/apovitabe/www/app/code/brainworx/medipimsync/Controller/Adminhtml/Sync/Edit.php(52): Magento\Backend\Model\View\Result\Page\Interceptor-&gt;setActiveMenu('Brainworx_Medip...')
#20 /data/sites/web/apovitabe/www/app/code/brainworx/medipimsync/Controller/Adminhtml/Sync/Edit.php(87): brainworx\medipimsync\Controller\Adminhtml\Sync\Edit-&gt;_initAction()
#21 /data/sites/web/apovitabe/www/var/generation/brainworx/medipimsync/Controller/Adminhtml/Sync/Edit/Interceptor.php(24): brainworx\medipimsync\Controller\Adminhtml\Sync\Edit-&gt;execute()
#22 /data/sites/web/apovitabe/www/vendor/magento/framework/App/Action/Action.php(102): brainworx\medipimsync\Controller\Adminhtml\Sync\Edit\Interceptor-&gt;execute()
#23 /data/sites/web/apovitabe/www/vendor/magento/module-backend/App/AbstractAction.php(226): Magento\Framework\App\Action\Action-&gt;dispatch(Object(Magento\Framework\App\Request\Http))
#24 /data/sites/web/apovitabe/www/vendor/magento/framework/Interception/Interceptor.php(74): Magento\Backend\App\AbstractAction-&gt;dispatch(Object(Magento\Framework\App\Request\Http))
#25 /data/sites/web/apovitabe/www/vendor/magento/framework/Interception/Chain/Chain.php(70): brainworx\medipimsync\Controller\Adminhtml\Sync\Edit\Interceptor-&gt;___callParent('dispatch', Array)
#26 /data/sites/web/apovitabe/www/vendor/magento/framework/Interception/Chain/Chain.php(63): Magento\Framework\Interception\Chain\Chain-&gt;invokeNext('brainworx\\medip...', 'dispatch', Object(brainworx\medipimsync\Controller\Adminhtml\Sync\Edit\Interceptor), Array, 'adminAuthentica...')
</code></pre>

<p><strong><em>Setup:</em></strong></p>

<p><strong>registion.php</strong></p>

<pre><code>\Magento\Framework\Component\ComponentRegistrar::register(
        \Magento\Framework\Component\ComponentRegistrar::MODULE,
        'brainworx_medipimsync',
        __DIR__
);
</code></pre>

<p><strong>etc/Module.xml</strong></p>

<pre><code>&lt;?xml version="1.0"?&gt;
    &lt;config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Module/etc/module.xsd"&gt;
        &lt;module name="brainworx_medipimsync" setup_version="1.0.4" /&gt;
    &lt;/config&gt;
</code></pre>

<p><strong>Form class exists:</strong> app\code\brainworx\medipimsync\Block\Adminhtml\Sync\Edit\Form.php</p>

<pre><code>namespace brainworx\medipimsync\Block\Adminhtml\Sync\Edit;

use Magento\Backend\Block\Template\Context;
use Magento\Framework\Registry;
use Magento\Framework\Data\FormFactory;
use Magento\Store\Model\System\Store;
use Magento\Backend\Model\Auth\Session;

/**
 * Adminhtml sync edit form
 */
class Form extends \Magento\Backend\Block\Widget\Form\Generic
{

    /**
     * @var \Magento\Store\Model\System\Store
     */
    protected $_systemStore;
    protected $_loginUser;

    /**
     * @param \Magento\Backend\Block\Template\Context $context
     * @param \Magento\Framework\Registry $registry
     * @param \Magento\Framework\Data\FormFactory $formFactory
     * @param \Magento\Cms\Model\Wysiwyg\Config $wysiwygConfig
     * @param \Magento\Store\Model\System\Store $systemStore
     * @param array $data
     * @param \Magento\backend\Model\Auth\Session $authSession
     */
    public function __construct(
            Context $context,Registry $registry,FormFactory $formFactory,Store $systemStore,
            array $data = [],Session $authSession
    ) {
        $this-&gt;_systemStore = $systemStore;
        $this-&gt;_loginUser = $authSession-&gt;getUser()-&gt;getUsername();
        parent::__construct($context, $registry, $formFactory, $data);
    }

    /**
     * Init form
     *
     * @return void
     */
    protected function _construct()
    {
        parent::_construct();
        $this-&gt;setId('sync_form');
        $this-&gt;setTitle(__('Sync Information'));
    }

    /**
     * Prepare form
     *
     * @return $this
     */
    protected function _prepareForm()
    {       
        /** @var \brainworx\medipimsync\Model\Sync $model */
        $model = $this-&gt;_coreRegistry-&gt;registry('medipimsync_sync');

        /** @var \Magento\Framework\Data\Form $form */
        $form = $this-&gt;_formFactory-&gt;create(
                ['data' =&gt; ['id' =&gt; 'edit_form','action' =&gt; $this-&gt;getData('action'), 'method' =&gt; 'post']]
        );

        $form-&gt;setHtmlIdPrefix('sync_');

        $fieldset = $form-&gt;addFieldset(
                'base_fieldset',
                ['legend' =&gt; __('General Information'), 'class' =&gt; 'fieldset-wide']
        );

        $fieldset-&gt;addField(
                'title',
                'text',
                ['name' =&gt; 'user', 'label' =&gt; __('User'), 'title' =&gt; __('User'), 'required' =&gt; true,
                        'value' =&gt; $this-&gt;_loginUser , 'readonly' =&gt; true
                ]
        );

        $fieldset-&gt;addField(
                'entity',
                'select',
                [
                        'label' =&gt; __('Entity'),
                        'title' =&gt; __('Entity'),
                        'name' =&gt; 'entity',
                        'required' =&gt; true,
                        'options' =&gt; ['PROD' =&gt; __('Products'), 'CAT' =&gt; __('Categories')]
                ]
        );

        //$form-&gt;setValues($model-&gt;getData());
        $form-&gt;setUseContainer(true);
        $this-&gt;setForm($form);

        return parent::_prepareForm();
    }
}
</code></pre>

<p><strong>edit class</strong>
Also the edit class containing the form
app\code\brainworx\medipimsync\Block\Adminhtml\Sync\Edit.php</p>

<pre><code>namespace brainworx\medipimsync\Block\Adminhtml\Sync;

class Edit extends \Magento\Backend\Block\Widget\Form\Container
{
    /**
     * Core registry
     *
     * @var \Magento\Framework\Registry
     */
    protected $_coreRegistry = null;

    /**
     * @param \Magento\Backend\Block\Widget\Context $context
     * @param \Magento\Framework\Registry $registry
     * @param array $data
     */
    public function __construct(
            \Magento\Backend\Block\Widget\Context $context,
            \Magento\Framework\Registry $registry,
            array $data = []
    ) {
        $this-&gt;_coreRegistry = $registry;
        parent::__construct($context, $data);
    }

    /**
     * Initialize blog post edit block
     *
     * @return void
     */
    protected function _construct()
    {
        $this-&gt;_objectId = 'sync_id';
        $this-&gt;_blockGroup = 'brainworx_medipimsync';
        $this-&gt;_controller = 'adminhtml_sync';

        parent::_construct();

        if ($this-&gt;_isAllowedAction('Brainworx_Medipimsync::save')) {
            $this-&gt;buttonList-&gt;update('save', 'label', __('Creatae new'));
            $this-&gt;buttonList-&gt;add(
                    'saveandcontinue',
                    [
                            'label' =&gt; __('Save and Continue Edit'),
                            'class' =&gt; 'save',
                            'data_attribute' =&gt; [
                                    'mage-init' =&gt; [
                                            'button' =&gt; ['event' =&gt; 'saveAndContinueEdit', 'target' =&gt; '#edit_form'],
                                    ],
                            ]
                    ],
                    -100
            );
        } else {
            $this-&gt;buttonList-&gt;remove('save');
        }
    }

    /**
     * Retrieve text for header element depending on loaded post
     *
     * @return \Magento\Framework\Phrase
     */
    public function getHeaderText()
    {
        if ($this-&gt;_coreRegistry-&gt;registry('medipim_sync')-&gt;getId()) {
            return __("Edit Sync '%1'", $this-&gt;escapeHtml($this-&gt;_coreRegistry-&gt;registry('medipimsync_sync')-&gt;getTitle()));
        } else {
            return __('New Sync');
        }
    }

    /**
     * Check permission for passed action
     *
     * @param string $resourceId
     * @return bool
     */
    protected function _isAllowedAction($resourceId)
    {
        return $this-&gt;_authorization-&gt;isAllowed($resourceId);
    }

    /**
     * Getter of url for "Save and Continue" button
     * tab_id will be replaced by desired by JS later
     *
     * @return string
     */
    protected function _getSaveAndContinueUrl()
    {
        return $this-&gt;getUrl('medipimsync/*/save', ['_current' =&gt; true, 'back' =&gt; 'edit', 'active_tab' =&gt; '']);
    }
}
</code></pre>

<p><strong>Layout file</strong>
And the layout file loading the edit class: view/adminhtml/layout/medipimsync_sync_edit.xml</p>

<pre><code>&lt;page xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:View/Layout/etc/page_configuration.xsd"&gt;
    &lt;update handle="editor"/&gt;
    &lt;body&gt;
        &lt;referenceContainer name="content"&gt;
            &lt;block class="brainworx\medipimsync\Block\Adminhtml\Sync\Edit" name="medipimsync_sync_edit"/&gt;
        &lt;/referenceContainer&gt;
    &lt;/body&gt;
&lt;/page&gt;
</code></pre>

<p><em>Thanks for the help!</em></p>