First thing I tried, and tried again now. No luck.If you have another profile try switching to that and then back to yours.
Seems like I'm not the only one experience this, though: https://discussions.apple.com/thread/250434813?answerId=252102286022#252102286022
I might try that, eventually. For now I'm just avoiding browsing on Netflix...I have the 4K, also with the latest tvOS. Maybe I just lucked out.
You could try uninstalling the Netflix app, rebooting the Apple TV, and then reinstalling...