Server logs please. If it is the auto migration failing and locks the DVR out, I have a development build to send to you
For logs see
https://support.plex.tv/articles/201643703-reporting-issues-with-plex-media-server/
restart the server to get fresh logs
then attempt to go to server settings for live TV and DVR and delete the DVR and recreate it
if issues arise, get the details and download logs and attach here
https://support.plex.tv/articles/200250417-plex-media-server-log-files/
