airtag doesn't work after battery change

Batteries with child-guard “bitterant” coatings indeed do NOT work.

(And all the Duracells I’ve see DO have the coating)

Buy a set of batteries without the bittterant coating.

How to replace the battery in your AirTag - Apple Support

You’ll know it’s “good” because the AirTag will “beep” as soon as the cover causes electrical contact with a good battery to be “made.”

I have the same problem and replaced the battery with an Energizer without the coating. It still doesn't work. I can get the serial number by holding at the top of my iPhone 13, but that's all it does. We bought it in December so it lasted 5 months.