Oddly, the solution is to manually update the Apple TV software version, not the Netflix app. I had my Apple TV set to automatically update its software version, but because of this problem I learned it doesn't always do that. I had to skip around the automatic part to force a manual update of the latest Apple TV software.
After that was done, Netflix loaded just fine. Working perfectly now.
Had tried tons of other things, even more than you before that. But the trick is that Netflix app had automatically updated, but the Apple TV software hadn't. Nothing was going to work until the Apple TV software was forced to update.