Please view this faq for detail instructions.
Usually app can detect which generation of Airpods you have. However it can make mistake. You can set it manually (see below). And then reconnect Airpods. If the setting is greyed out it means that your phone hardware doesn't support airpods 2. Currently the only solution is to buy Airpods Tracker.
Please view this faq for additional steps instructions.
You will see popup window (below). Wait a few seconds and you will see battery level showing up.
If you don't see popup window your earbuds might not be authentic Apple product. Please use this faq to verify if you have fakes or authentic product. If you see popup window but it says "waiting for battery data", please follow this faq for troubleshooting.