Comes on but no sound

Also If you had a flat battery the cat might need to be recoded for whichever speaker system and head unit are installed. Btw this is vw stock audio system right. If not you might be missing required wiring harness to make it compatible or an uadaptor to ensure a 3rd party head unit is compatible. Pictures of the head unit and the fuse boxes would help but also a video of what happens when you Try to use the functions so we can see exactly what happens. Also investing in a fuse tester would be well worth it and I can find the fuse assignments for your car but I need the car year the model the engine size and if it's 4 motion or not. Also check the date manufacture for your car in the front section of the instruction booklet. Otherwise giving your Vin can help me search through vw Elsa win program and also I have an account at Mitchell diy with the electrical guides and can post the appropriate fuse and wiring diagrams for your car and the wiring from head unit along with which fuses or relays are related.