There could be several reasons why your Audi MMI screen is not working. Here are some possible causes:

Battery voltage: If the car audio navigation system battery voltage is low, it can cause the MMI screen to go blank or display an error message. Make sure the battery is fully charged and the voltage is stable.

Power source: The MMI screen may not be getting enough power from the vehicle's electrical system. Check the fuses and wiring connections to ensure they are in good condition.

Software issue: The Audi screen for sale MMI screen may have a software glitch or error that is preventing it from functioning properly. Try restarting the system or performing a software update.

Hardware failure: The MMI screen may have a hardware failure, such as a faulty screen or connection issue. In this case, you may need to take your vehicle to a qualified mechanic or dealership for repair.

User error: Finally, make sure you are using the MMI system correctly. Refer to your audi Q5 screen vehicle's owner's manual for instructions on how to properly operate the MMI system.