Missing tuner channels FritzBox

[Olli]

Maybe try one of the Fast Scan at the bottom:
(you have to select them twice..)

wait a few seconds, scroll down again and select your Network..

If the lineup is not correct, see also:

Reporting Plex DVR Lineup Inaccuracies

How to Report EPG Errors Are you noticing inaccuracies with the electronic program guide in Plex Live TV & DVR? (PMS Version 1.21.0.3711 or newer.) You can help us quickly report problems to our metadata partner by providing us with information on your channel lineup. While we will make every effort to resolve lineup inaccuracies, we can’t provide any guarantees, estimated time for resolution, or personally respond to every report. Thanks for taking the time to help improve the Plex EPG for your…