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If you have the software for the WinTV installed you should uninstall it. As the note at the bottom of the Supported Tuners page indicates it can cause interference with Plex’s ability to access the tuner. Only install the driver for the tuner. See: https://support.plex.tv/articles/225877427-supported-dvr-tuners-and-antennas/
Duplicate channel identifiers is the issue. I had the same problem. Plex is incorrectly identifying available services.
