Airtag doesn't show up in FindMy and I can't reconnect it

I have an Airtag with a brand new battery. It has been connected to my account before, but I have removed it and deleted it from my account. Now I want to connect it again. I have done the resetting procedure, but all the chimes sound the same. It doesn't show up in the list of items so I can't remove it. And the iPhone doesn't recognize it so I can't connect it.