Key Battery and Synchronisation

[N8e]

I received a notification in the cockpit to say my car key battery needed changing which I've done.

1. How do I get rid of the notification as it still keeps coming up when I turn the ignition?
2. Since I changed the battery the key no longer locks/unlocks the door so I read the booklet which instructed how to resynchronise the car key but that hasn't worked. Any suggestions on how to resolve this?

 

[NHN]

On which chassis.

Usually it resyncs with ignition on off, try starting the car & pressing a lock button on the key.

 

[northpole]

if it doesn't only re-registering the key will work.

 

[AlS3BE]

I had something similar on my old a6 and it was the new battery.
First new battery was cheapest battery I could find and message stayed on dash and wasn’t locking/unlocking then tried a second as it was a twin pack still the same. Got another battery this time a Duracell and everything worked fine.
I later put both batteries on a multimeter and Duracell was higher voltage than the cheap brand.