it looks like my airtag does not connect to the battery, I tried 2 different ones

Many button batteries have a ‘bittering’ coating to discourage small children from putting them in their mouths.

Unfortunately, that coating can interfere with the connection.

Make sure you use batteries that are not coated.

Cody2022 wrote:

is it possible to remove the coating?

Probably, but the denatonium benzoate (what seems to be used by Duracell) is intended to persist.

Ask Duracell if they have an official and preferred means to remove the coating.

There are published discussions around the ’net that claim ways to remove the bitterant, but I have none of those batteries available to test. If I had those batteries, I’m not fond of experimenting on lithium batteries, and would not recommend anyone experimenting with various chemicals on lithium batteries. Damaged lithium batteries can get very hot very quickly. And if they don’t deflagrate, I’d still rather not have the battery degrade or corrode and fail, or corrode and leak, due to some chemical exposure or another.

Other stuff refuses to work with those bitterant-coated batteries.

Garmin suggests re-positioning (rotating) the battery, as an alternative to attempting bitterant removal:

… https://support.garmin.com/en-US/?faq=2f9Dc8X1Dy8fDGEXYxtMM9

Or get the non-bitterant batteries.

If you are using Duracell batteries they are likely the culprit because they do coat their batteries with bitterant and users have complained about them not working with AirTags. The coatings are supposed to deter children from putting them n their mouthes and choking.

Hard to do so I use Energizer batteries and they work fine. Any brand that does not specify a bitterant coating should also work.