After Kinetic Upgrade can no longer add new or view existing attachments

After the upgrade our users are unable to view some existing attachments or add new ones. We get an error.

I feel like I may have read something in the documentation about this, but I can’t find it now, of course. Anyone have any idea what to do?!

I had a similar issue with attachments when upgrade from 10.2.300 to 10.2.700, in my case the problem was caused by the empty field XFileRef.DocTypeID as shown in your screenshot.
I made this for fixit:

In Attachment Type Maintenance:
Set storage type to File System
Set Base URI to \\yoursharedstorage\
Set Transfer Type to File Transfer Using Service
Check Enable and Company Default

Verify that in Document Type Maintenance your Type ID exists.
Type ID: CustomerPDF
Description: My Customer PDF
Storage Type: Attachment Link
File Tranfer Mode: Alway Use Company Level Settings
BaseURL: \\yoursharedstorage\CustomerPDF

3.- Fix empty XFileRef.DocTypeID records with DMT or ServiceConnect (I use this one).

4.- Test.