cannot be used to unlock this iphone

Hello,

If you try to activate a second-hand iPhone/iPad and see an error popping up saying, "Your Apple ID cannot be used to unlock this iPhone/iPad", it usually means that this iOS device is still logged in with the previous owner's credentials. Therefore, you can't use your own Apple ID to unlock this device.Dec 16, 2021

See this:

Turn off Find My iPhone Activation Lock

Good luck.