Finally, here are some recent discussions that all point to similar issues - not being able to scan/re-setup.
[HELP] Postal code error while configuring DVR - Live TV & DVR - Plex Forum
Rescan doesn’t work on new interface - Live TV & DVR - Plex Forum
Lost of bunch of channels from DVR, rescan not working - UK TV - Live TV & DVR - Plex Forum
Plex finds 978 channels during scan, but lists only 19-20 - Live TV & DVR - Plex Forum
