My AirTag required a new battery. After changing it now isn’t recognised as mine. My phone is unable to connect to it tho occasionally it shows as AirTag moving with me. I’ve tried disconnecting, Wi-Fi, Bluetooth but no joy.
AirTag
In practice, just replacing the battery, should not cause the pairing between the AirTag and your iPhone to be "lost." However, anything can happen and this is not necessarily an unusual case.
Based on what you provided, your tag "believes" it may now associated with another Apple ID. To try to rectify this, I suggest that you reset your tag: How to reset your AirTag - Apple Support
In practice, just replacing the battery, should not cause the pairing between the AirTag and your iPhone to be "lost." However, anything can happen and this is not necessarily an unusual case.
Based on what you provided, your tag "believes" it may now associated with another Apple ID. To try to rectify this, I suggest that you reset your tag: How to reset your AirTag - Apple Support
Reconnecting AirTag after battery replacement
