PMS can’t find your media (drive/network share isn’t mounted, media moved or removed) and it’s pending complete deletion (removal from your library). Were you to Empty Trash, it would be fully removed.
I recommend you look at the series Info. Particular interest is the directory & file path. Make sure everything still exists & is accessible.
If the directory was moved or accidentally renamed, updating your libraries, after being corrected will remove the trash can and all will be normal. If you have just moved the media to a new location, a normal update will find the new location, retain the metadata, and remove the trash can.
