Lost iPhone
How to connect my old AirTag to my new phone? I lost my old iPhone it’s still connected to my old Apple ID.
iPhone SE
Question marked as
Why did you create a new ID? You can use the old ID with any new device.
From: How to reset your AirTag - Apple Support
"An AirTag can be associated with one Apple ID. If you want to use an AirTag that someone else (that can mean you with a different ID) has used, they need to remove the AirTag from their Apple ID first as described in this support article —> If an item or device is connected to another Apple ID - Apple Support .