Plex DVR, Trying to watch Live TV but get error "Unable to tune channel (no parts)"

Could you give details of your setup and list of channels and territory / guide

and get some logs to see what the error is

Please ensure debug logging is enabled
See https://support.plex.tv/articles/201643703-reporting-issues-with-plex-media-server/

restart the server at this point to get fresh logs created

Reproduce the problem and test several channels - and note down details and times of tests and results

and get the server logs
See https://support.plex.tv/articles/200250417-plex-media-server-log-files/

Attach here with the requested info