Would this be an issue with the XLSForm? I have ~50 forms created over the last couple years (aka, some on the most recent template, and others not). They are all having the same issue with querying Esri for a Feature Report.
It is important to note that I (and I assume others?) can still write data to the Feature Service. It's only when we try generating a report that the error pops up:
Also of note, I am on Enterprise. I don't have a test environment on AGO, but I believe all S123 Feature Reports query the same service, so the error likely is happening there as well?