Cvc-elt.1: Cannot Find The Declaration Of Element 'soap:Envelope'
<p>Currently I'm using XSD for SOAP XML, but when I run my SOAP XML and XSD on <a href="http://www.freeformatter.com/xml-validator-xsd.html" rel="noreferrer">FREEFORMATTER.COM</a>, I get this error:</p>

<blockquote>
  <p>Cvc-elt.1: Cannot Find The Declaration Of Element 'soap:Envelope'.. Line '1', Column '170'</p>
</blockquote>

<p><strong>This is my SOAP XML:</strong></p>

<pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
&lt;soap:Envelope xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
               xmlns:xsd="http://www.w3.org/2001/XMLSchema" 
               xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/"&gt;
  &lt;soap:Body&gt;
    &lt;Cancel_OrderLine xmlns="http://tempuri.org/"&gt;
      &lt;Data&gt;
        &lt;Delivery&gt;
          &lt;Delivery_No&gt;1605000194&lt;/Delivery_No&gt;
          &lt;Reason&gt;qwertyu&lt;/Reason&gt;
        &lt;/Delivery&gt;
        &lt;Delivery&gt;
          &lt;Delivery_No&gt;1605000194&lt;/Delivery_No&gt;
          &lt;Reason&gt;qwerty&lt;/Reason&gt;
        &lt;/Delivery&gt;
      &lt;/Data&gt;
    &lt;/Cancel_OrderLine&gt;
  &lt;/soap:Body&gt;
&lt;/soap:Envelope&gt;
</code></pre>

<p><strong>This is my XSD:</strong></p>

<pre><code>&lt;xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
           xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
           xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/"&gt;
  &lt;xs:element name="Cancel_OrderLineReq"&gt;
    &lt;xs:complexType&gt;
      &lt;xs:sequence&gt;
        &lt;xs:element name="Data"&gt;
          &lt;xs:complexType&gt;
            &lt;xs:sequence&gt;
              &lt;xs:element name="Delivery" maxOccurs="unbounded" minOccurs="0"&gt;
                &lt;xs:complexType&gt;
                  &lt;xs:sequence&gt;
                    &lt;xs:element type="xs:int" name="Delivery_No"/&gt;
                    &lt;xs:element type="xs:string" name="Reason"/&gt;
                  &lt;/xs:sequence&gt;
                &lt;/xs:complexType&gt;
              &lt;/xs:element&gt;
            &lt;/xs:sequence&gt;
          &lt;/xs:complexType&gt;
        &lt;/xs:element&gt;
      &lt;/xs:sequence&gt;
    &lt;/xs:complexType&gt;
  &lt;/xs:element&gt;
&lt;/xs:schema&gt;
</code></pre>

<p>What should I do to eliminate the error?</p>