I'm not sure if this is the same problem I was having. However, about a year ago I had the same random electrical issues. It turns out that the battery connectors were loose. You might want to check them out.

 

2002 TT convertible, I had the car at a detail shop and got it back and things seem not to work. the trunk and gas lids are not operating and the door lock process does not make the beep sound and the small red light on the door does not go on. I checked a couple of fuses and found them all OK. I am at a loss. They all worked fine before getting the car cleaned. I am a loss.

 

thank you so much for this information! I had tried everything and nothing worked until I read your suggestion and tried that and it worked!!! Crazy but thank you

 

Worked a treat, loosing my **** in a petrol station looking for a fuse, calmed down had a quick Google and this worked perfectly. Ivwas very close to using a screwdriver to open it.