I see that the latest version of plex server will run ad detection on libraries other than just native DVR recordings. I have selected the option to run ad detection in a new library I created. I also set the Library setting "Generate ad video markers " to “As scheduled task and when media is added”. How do I get it to initiate the ad detection? I placed a new .ts file in the folder of the library but it did not start detection. I am pretty new to Plex so maybe I am not understanding something about how this is supposed to work?
I’ve done all the things. Plex is not marking any ads on any shows that weren’t recorded using the Plex DVR functionality.
Check this setting in your library’s advanced settings:

Ensure it is set to “For all items.”
Then, manually analyze an episode (or the entire show).
