Wordpress form not sending file attachement to CRM - wordpress

Question

I may have hit my limit on knowledge on this :-)
I have a wordpress form to integrate with a CRM. When submitted it sends correctly all the data from the form apart from the file attachment. This won't upload.
My code is below... The varchar ID's match the CRM special fields and work fine and so does the re-direct to thank you page.
Am I missing something here to help upload the attachment, or is it an error and just not talking to the CRM's backend?
Many thanks
<form id="HubForm" action="https://www.CRM-DOMAIN-NAME/Api/FormAdd" method="post">
<input type="hidden" name="ClientId" value="123"><input type="hidden" name="FormTypeId" value="123">
<input type="hidden" name="redirect" value="https://www.CLIENTS-DOMAIN-NAME.co.uk/applied/">
<input id="firstname" class="emrform" name="firstname" type="text" placeholder="First Name" required /><br>
<input id="lastname" class="emrform" name="lastname" type="text" placeholder="Last Name" required /><br>
<input id="email" class="emrform" name="varchar3" type="text" placeholder="Phone number" required /><br>
<input id="firstname" class="emrform" name="email" type="text" placeholder="Email" required /><br> Upload your CV<br><input id="fileUpload" class="emrform" name="fileUpload" type="file" accept=".pdf,.doc,.docx" /><br> Interested in receiving further
emails?
<br>
<input type="radio" name="varchar4" value="yes" id="varchar4" checked> YES<br>
<input type="radio" name="varchar4" value="no" id="varchar4"> no<br>
<br>
<br>
<textarea class="emrform" id="textarea" rows="5" name="varchar2" placeholder="Message details..."></textarea>
<br>
<input type="submit" class="emrbtn emrbtn-primary" value="Submit"></form>
<div id="HubFormResult">