Scheduled export created by an embed user fails with "Permission denied"

Summary: Scheduled exports and email alerts created by an embedded (JWT) user can start failing with a Permission denied error, even though that user can still open and view the same workbook in the embed. The usual cause is that the user’s team membership changed when they last opened a different embed URL, and their current team no longer has access to the workbook. What you may see: An email alert or scheduled export that worked for days or weeks fails, then may work again, then fails again.