Audi=No fault code, no idea
The only thing i can suggest thats a cheap option is to remove the battery's, clean with a tissue as well as the contacts in the key and re fit holding them in the tissue. The battery has a very low voltage /current and even grease from fingers can give a very bad contact. i cant believe both keys have failed at the same time, seems to much of a coincidence.
Ibis white Revo S3 and now matching Vivaro LWB HR 2900 :-)
Many people are alive because its illegal to shoot them.