Hey there!
Since you said you’ve gone through all the steps already, You might already be familiar with these articles:
Use AirPods with your Mac:
https://support.apple.com/guide/mac-help/use-airpods-with-your-mac-mchld2f124d1/11.0/mac/11.0
If your AirPods won’t connect:
https://support.apple.com/en-us/HT207974
Reset your AirPods:
https://support.apple.com/en-us/HT209463
I’ll assume you’ve already forgot other connected devices, restarted, tried connecting again, making sure fully charged etc. from what you said.
And of course checking software compatibility and making sure it’s up to date and all.
There could be a number causes from software/hardware/network environment, and even an interface change, etc.
I’d probably try the steps in this article here, maybe a quick fix, though I haven’t yet tested it yet on the new OS, still may help resetting the SMC, and/or the Bluetooth Module, as in the article:
https://www.macrumors.com/how-to/reset-mac-bluetooth-module/amp/
Otherwise, can you give more specifics? What shows up in preferences, if other Bluetooth devices connect fine, if these AirPods do or don’t connect to other devices, If OTHER AirPods connect to the same Mac (If able to test), what devices you normally have connected? And finally if the same happens in safe boot and/or another user?
Thanks, that might help to diagnose but hopefully one of those suggestions helped!