I had the same issue with the air tag not connecting to my phone and I tried everything that everyone is talking about.
it has been a week and still nothing and then I finally got it to connect to my phone. Here are the steps I did
1) you have to delete all Bluetooth connection and if you have a watch, you will have to unpair it in the watch app ( once you delete the watch, you will be able to restore it when you pair later)
2) turn off the Bluetooth
3) go into setting and click on your name, that will take you to your Apple ID, click on find my and turn it off
4) reboot your phone. Once the phone has rebooted, turn on your Bluetooth and find my phone
5) go to find my app and pair your air tag
After trying for a week and nothing, after following the steps above, it finally work! 😃