Having the same issue as https://community.playfab.com/questions/66979/event-export-not-working-for-amazon-s3.html?childToView=67370#comment-67370 (can't seem to post there)
When attempting to modify an existing, working event export to S3, or attempting to create a new one, I'm always met with the error:
The provided bucket name or credentials are invalid.
Tried with a new bucket as well, but same issue. The credentials are valid, which should be confirmed by failure to edit the working event.