Hey @cadoad, welcome to the Community!
Ah yes, it sounds like you’re running into the bug mentioned on this related topic:
I’ve added you to the list of users being affected by that so we can notify you by email as soon as it’s resolved. We’ll post any news on that front in the related topic so please do subscribe to it for future updates on that!
There’s a workaround mentioned on that post about moving the S3 bucket to the "N California" region which should allow it to be seen by the Zap.
If you’ve already tried that and it didn’t work, I remember an instance from when I worked on the Support team where a customer changed the policy/permissions to make the condition keys less specific and got it working. If you give that a try and it does the trick please let us know!