Key Fob Doesnt work after changing battery. Even old battery doesnt help.
 

I changed to a new battery because the A6 said this needed to be done. Now the key fob does not work. I put the old battery back in and that doesnt work either.Help!

I'm not absolutely sure, but you might just need to re-sync your remote to the car again?

Tread for how to reprogram key fob
 

3 step instructions to sync your dead key fob is in this thread on the board:

https://www.audiworld.com/forums/tt-...ement-1954050/

Go to Roos-Tech website under wiki-tech
and find this article since it's too long to cut/paste:
It will discuss exact steps to re-program

Audi TT (8N) Central Locking