Assuming that you have checked the fuses, look for a loose connection in the wiring harness. I believe that there is a connector in the trunk area that may have come loose.
signal lights not working.
Just because I had one in the past (2004 malibu) I would say that I has something to do with the fuse that works for the turn signal and brake light. Because for them both not to be working I would doubt that it was a bulb. Just my opinion. Of course you should get it looked at.
An open ground or a short to ground when the signal is on. Usually a bad bulb.
Either hand signal or check and replace your fuses and turn signal bulbs.
either dimmer switch or blown fuse If you are saying that the tail brake lights are working but the third brake light is not....It may be a defective turn signal switch in the steering column.
When the signal lights are not working on a car, there are a couple of things that could be going on. One could be that the bulb needs to be replaced. The other possibility is that the signal relay needs to be replaced.
It's the turn signal indicator-located behind the hazard lights.You have to take it out and replace it.
Trun signal lights do not come on at all not on dash or outside
bad fuse or hazard switch
Signal lights staying on withot flashing indicates either front or rear signal bulb not working on the Audi
see your dealer about a recall for flasher
Multifunction lever at the left side of steering wheel?