To correct this, you may need to restore defaults for Plex Web:
Settings → Plex Web → Debug → Reset Defaults
This doesn’t affect your server configuration, it just clears all of Plex Web’s config data; you’ll have to reconfigure Plex Web after doing this (pick your default server, select pinned libraries, etc…).
As far as I know, you can only filter by manually-created collections using that filter (or the same option in Advanced Filters). At least, that’s how it works on my own server.
