It is hard to analyze with limited logs - previous tuner service logs may show additional information, as may the main Plex server logs (e.g. I’ve seen it detect the tuner in the main server logs even when no tuner is shown in the web interface.)
Lacking additional information, have you tried a full reboot of the Win server to see if it will release the port? Also, take a look at this thread where people have had success with restoring their DVR by deleting the tv.plex.*.* files when faced with similar symptoms.
