Gearbox Problem Audi A3 2015

[Valon]

Hi dear friend, lately I have been receiving this message in my car Audi A3 TDI 1.6 Diesel - Stronic. 2015-16 Model
(gearbox please press brake pedal and select gear again)
while the car does not start moving when I have this message
The car has all the services done properly, even now it has 300k KM

What can it be, what should I do?

[Steve Q]

When was the gearbox oil last changed? Degrading gearbox oil in the s tronic box can affect its ability to select gears. 

Also does the gear selector area light up properly? 

I'd also recommend a diagnostic check to see if any fault codes flag up