Add-on "appears to be corrupt" when trying to install my add-on's .xpi file in Firefox
<p>I am trying to install an extension in Firefox 45 (same happens with Firefox 49), but Firefox does not allow me to do that, indicating that </p>

<pre class="lang-none prettyprint-override"><code>This add-on could not be installed because it appears to be corrupt. 
</code></pre>

<p>The way I am trying to install it is simply by <strong>dragging the .xpi file</strong> our team developed, into the Firefox window. This extension is based on <a href="https://github.com/bard/mozrepl/" rel="noreferrer">MozRepl</a>, but with some improvements.</p>

<p>Previously, I tried to install it but I couldn't as it was not signed (extensions in Firefox versions from 43 onwards require signing). I followed every step in order to sign it, according to this post: <a href="https://developer.mozilla.org/en/docs/Signing_a_XPI" rel="noreferrer">Signing a XPI</a>. I am almost certain I could sign it correctly, but now the error Firefox displays is different: "This add-on could not be installed because it appears to be corrupt."</p>

<p><a href="https://i.stack.imgur.com/gzmzb.png" rel="noreferrer"><img src="https://i.stack.imgur.com/gzmzb.png" alt="enter image description here"></a></p>

<p>It seems that I am not creating the .xpi file correctly, but I am not sure which is the correct structure it should have. I tried different folder structures, but with no success. </p>

<p>Also, I checked the Browser Console to see what error is logged in, but I didn't found it really helpful. Here it is:</p>

<p><a href="https://i.stack.imgur.com/jhMBT.png" rel="noreferrer"><img src="https://i.stack.imgur.com/jhMBT.png" alt="enter image description here"></a></p>

<p><a href="https://drive.google.com/file/d/0B7KHv4DP9WZiUjB2REZ3Wk1Hcm8/view?usp=sharing" rel="noreferrer">Here</a> is a link to the .xpi file in case you want to check its content. Note that I tried moving the files manifest.mf, zigbert.rsa and zigbert.sf outside the META-INF folder, but it didn't work either.</p>

<p>Has anyone stumbled across an error like this when trying to install an add-on? Any ideas of what maybe happening?</p>