SharePoint hosted Office 365 App manifest (admin center can't read sharepoint URLs)

I have been struggling to get Admin Center to publish a manifest for a fully working SharePoint hosted Office 365 app.

Does anoyone here know why Admin center cannot accept SharePoint URLs in a Word add-in manifest?

This is my manifest (altered for privacy)

<?xml version="1.0" encoding="utf-8"?>
<OfficeApp xmlns="http://schemas.microsoft.com/office/appforoffice/1.1" 
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
    xsi:type="TaskPaneApp">
  <Id>A8A45AA7-87F5-4A8B-B10C-2FDB853BFA46</Id>
  <Version>1.3</Version>
  <ProviderName>Company</ProviderName>
  <DefaultLocale>EN-US</DefaultLocale>
  <DisplayName DefaultValue="Rapid Document Assembler"/>
  <Description DefaultValue="Company Document Assembly SharePoint"/>
  <IconUrl DefaultValue=
    "https://companyportal.sharepoint.com/sites/DocumentAssemblySite/PublishingImages/logo32x32.png"/>
 <AppDomains>
  <AppDomain>https://login.microsoftonline.com</AppDomain>
  <AppDomain>https://eadadfs.company.com</AppDomain>
  </AppDomains>
 <Hosts>
    <Host Name="Document"/>
    <Host Name="Workbook"/>
  </Hosts>
  <DefaultSettings>
    <SourceLocation DefaultValue="https://companyportal.sharepoint.com/sites/DocumentAssemblySite/generated.aspx"/>
  </DefaultSettings>
  <Permissions>ReadWriteDocument</Permissions>
</OfficeApp>

When our SharePoint architect attempts to publish to Admin Center he gets this response:

Admin Centre rejected manifest url

 Surely there must be a way around this? The content the add-in serves comes from Sharepoint, and is commerically sensitive, so we cannot have a fully public, and open URL, the MFA offered by SharePoint is (or should be) perfect!