Key fob not working a4 b8
 

I have a Audi 2009 A4 B8, and the key fob stopped working it does not open or close the doors anymore. I have changed the key fob battery and still it does not work. I can se that the key fob sends a signal because the small light in the key fob turns red when i press a button. And i have checked all the fuses. Do you guys have any suggestions of what i can do to fix the problem.