To switch from TiVo DVR setup to the Gracenote DVR setup, it is necessary to Delete the DVR first. This action would also purge the EPG database files.
Is the issue that you did not delete and re-create the DVR ?
I expect there to be a banner in Plex Web when you are still running with the TiVo DVR setup.
There was a note about the need to delete the DVR here (point 6) Live TV EPG - The update you’ve been waiting for
