I'm referring to the pop-up window one can access by clicking just underneath the series title. The pop-up used to show ratings for each individual episode, but now only displays ".../10" in bright red for every episode.

EDIT: I think I jumped the gun. Some series are displaying imdb ratings. I guess I just found series that don't have that info available through Coollector. Nevermind.

To make sure that it's not a bug, click the IMDb icon and it'll take you to the episode IMDb page. There you'll be able to see if the episode has some ratings or none.

Stargate Atlantis had stopped displaying ratings. Today it's working again and I have no idea why. Yesterday I tried everything I could think of to get those ratings back, because I know I'd seen them displayed before. (Moving the backup folder, downloading a fresh copy of Coollector and generating a fresh empty backup folder... plus lots of other things.) My Mac somehow corrected the problem without my help. The glitch is definitely not Coollector's fault.

Yesterday the rating of many episodes has been updated, so I'm not completely sure but it's likely what has fixed the problem. Anyway it wasn't normal that Stargate Atlantis had zero ratings, definitively a bug, but most likely a bug on my side (the episode data on the server) rather than on your side (your computer). Sorry for the inconvenience, thank you for reporting.