I had a similar issue. My Apple TV was already set up with multiple profiles, and no parental controls or content restrictions set on the account level.
I turned it on and it had a sort of a welcome screen mentioning something like "Get Started" (as if it had just installed an update or something).
I went to watch Pluribus on the Apple TV app (which we'd already been watching) and it wouldn't show on the home screen. Selecting the show in a search said that it could not be shown due to a content restriction. I could locate it and even start playing the show on my iPhone, using the same iCloud account (again, no content restrictions enabled) and the Apple TV app.
I tried enabling and disabling content restrictions from my iPhone, no luck. I tried adding another adult profile to the Apple TV (which didn't have content restrictions enabled either), no luck. I tried messing with the Profiles in the Settings. I tried wiping out the Apple TV, still no luck. I ended up just using AirPlay to stream the show I wanted from my iPhone to the Apple TV until I was able to figure out the issue.
It turns out, the issue was the Apple TV app itself has its own content restriction settings for the profile(s). I'm not sure how it got enabled or why, but I was able to fix the issue by going to the following settings on the Apple TV device:
Settings > Apps > TV > Profiles > [Select Profile] > Content Restrictions (Set Up)
This is a different menu/options than the Settings > Profiles.
You then need to verify by scanning a code on your phone and logging in.
Then, you can adjust Filter Content for TV Shows and Movies. For some reason, TV Shows was set to TV-Y7 and so I changed to Allow All.