If a recurring or self scheduling workflow requires user-specific OAuth API Connector calls, it will fail after the initial run. This is because when a recurring event runs any time after the first time it has been scheduled, it runs as an admin (not a specific user) on the server. While the app can access any info stored normally in the database, OAuth credentials are user specific and can only be accessed by that user.

One potential workaround is to schedule recursive workflows to pre-authenticate and ensure the workflows run as that user.