Yes I let the engineer know and have heard back. With his help I figured out that the changes that were made don’t seem to apply to all Apple IDs that have already connected to your app before the changes were made and that the connection must be deleted for it to start working again.
To do this I had to go to https://appleid.apple.com, find the “Security” section, find the “APPS & WEBSITES USING APPLE ID” setting and click manage, then click on our app and click the “Stop using Apple ID” button.
Cheers,
Stefan