Our Collector ipads fail to upload attachments to portal, returning the above error. Android uploads work fine, we can retrieve pics from web maps right away. Switch the maps over to AGOL and the ipads upload attachments fine.
I did notice on our Portal that when i select to enable attachments, it will think for a minute then switch to 'attachments enabled' without the change notification pop-up that AGOL has. Also, in the view data tab there is no '(#)' next to the Show attachment field entry.
error messages and server manager snips below: