Audi Q2 fob key not opening door after battery replacement

[cobblers.keys]

Customer has been in saying she has bought a used Audi A1 from a private seller and the seller changed the battery with a Panasonic 2032 but since then the central locking hasn't worked. She took the car to a local garage who suggested she brings the key to me. I have just tested the key buttons on the xhorse frequency tester and checked the chip on the rw4plus. Everything seems ok but I changed the battery to a Renata 2023 just in case her battery wasn't powerful enough etc. however I told her that if it still doesn't work she will need to go to the Audi dealer to pair the key to the car. When she walked back to her car pressing the buttons still nothing happened. What would be the cause with this? Thanks 

[Cameron Avery]

May need resynching to the car.

 

[cobblers.keys]

Thanks for your help Cameron