With SeriesGuide 58 the data source for shows is changing to themoviedb.org (TMDb) away from TheTVDB.
After updating to version 58 SeriesGuide will try to find your shows on TMDB and migrate to TMDB data.
If a show or some of its episodes can not be found, a warning message is displayed above affected episodes:
What can you do about this?
If you just updated in the last few days, it may take up to a week for all shows to get migrated.
If only episodes of newer seasons are not found, it is possible that TMDB has a separate show entry for the newer episodes. Try to search for and add that newer show.
For anime, episodes might now be listed in a single season. Note: use the “Watched up to here” button after finding your last watched episode in that single season to quickly restore your progress.
To delete all not found episodes, remove the show and add it again. Make sure to set watched/collected any episodes based on the old data.
Other related issues:
Can no longer set watched on Trakt or Cloud
That show or episode might not have been found on TMDb (yet), see above. To check if a show was migrated, tap the TMDb link in the Details view. If it opens the TMDb website, the show was migrated.
It is also possible that a show on Trakt still uses TheTVDB data, which might group episodes into different seasons. E.g. for anime where TMDB typically uses a single season, but TheTVDB uses multiple seasons. You will have to wait until Trakt changes that show to use TMDB data (the Trakt website indicates the current data source of a show).
Show data is no longer updated
If a show can’t be found on TMDb, SeriesGuide will no longer update it. But it will remain in your library (note: once removed you can no longer add that show). Should it ever be added to TMDb in the future and its TVDB ID set as external ID, SeriesGuide will update it again.
You can check the TheTVDB ID under External IDs on TMDb when editing a show:
It should match the ID from the TheTVDB show page: