How to properly reset AirTag and remove from a client network?

airtag do not connect to networks their only means of communication is bluetooth, and bluetooth connects to 1 device, so if it do not show up on the ios device it was first paired with then it's no longer connected to anything

if you want to know more..

How to Remove AirTag From Your Apple ID Account Before Selling it

How to reset your AirTag - Apple Support

more

airtag prepare for sale - Google-

An Apple AirTag is not associated to a network, but to the owner's Apple Account. Only that owner can remove it from that account. No amount of resetting the tag will remove this association and Apple will not do so either.

The owner can register / deregister an AirTag to / from an Apple Account using either an iPhone or an iPad, but not a Mac. That’s because AirTags require proximity-based setup using Bluetooth and the Find My network, and macOS doesn’t support the pairing process or AirTag registration like iOS and iPadOS do.

Ref: Remove an AirTag or other item from Find My on iPhone - Apple Support

Bluetooth range is around 30meters

its not a matter what device it was paired with it’s a matter of what appleID it was paired with, all devices that use that appleID will be able to see it in the find my app

its the only app I know of which will work