The Movie Database wont pull content ratings

Naming of files can be critical and have found over the years to get a good result you must match the name exactly as it appears at IMDb or TMDB. So depending on your settings you need to check.
Have your agents set up correctly is also very important.

https://support.plex.tv/articles/naming-and-organizing-your-movie-media-files/

https://support.plex.tv/articles/200241558-agents/

If all fails the Fix match and IMDb ID can be used followed by Refresh metadata.

If you have named and structured your collection incorrectly Plex dance may be required.

  1. Move the files out of view from Plex
  2. Update the library
  3. Empty trash or Clean Bundles?
  4. Clean bundles or Empty Trash?
  5. Move the correctly named files back
  6. Update the library

You may think this is trivial but I can assure you it is far from it. Example: (Screen shot)

If when using Critic rating filter, I have found if you do not establish source Icons you have a Naming issue and need to repair your Collection.