Only Google namespaces are supported in XML feeds.
On this page
Reason why the issue is happening
In your XML, you define and use a namespace that’s not supported. Only the Google base namespace "http://base.google.com/ns/1.0" and "http://base.google.com/cns/1.0" for custom attributes are supported.
How to fix the issue
Remove any other namespace and the attributes referencing the namespace from your XML file.
Next steps
After making the requested changes, check that you've fixed the issue by making sure it's no longer listed on the "Needs attention" page.
Keep in mind: It may take some time for your change to be reflected on the "Needs attention" page.
Learn more about Product data specifications.