I bought a replacement right airpod pro (2nd gen) and It wont pair with each other or by itself.

I have the same issue which is how I ended up on this forum a few days back. I tried the same things you did, but with no joy. As a last resort I called Apple Support on Friday and we also tried a few things over the phone with no success. The support person suggested that I make a Genius appointment at my local Apple Store, which I did and visited there yesterday.

The Specialist at the Apple Store said that this was a known issue that has become apparent over the last couple of weeks - possibly due to a conflict between the versions of firmware running on the left and right AirPods and case. They couldn't swap my Airpods out with new a new set as my case is personalised, so they've retained my Airpods for now and will attempt to get everything synced and paired up over the next few days. The specialist also said that if they aren't able to get everything working, that I'll get a new Airpods set.

I suspect that this issue will be addressed in an upcoming firmware update. But, for now, if you're able to, I would recommend visiting your local Apple Store for assistance.