How to troubleshoot unresponsive controls in an Audi A2?

I have an Audi A2 and I've noticed that some of the controls, such as the buttons for the radio and air conditioning, are not responding. How can I troubleshoot and fix this issue?

First, check the fuse box for any blown fuses related to the controls. If they are all intact, try resetting the control unit by disconnecting the battery for a few minutes and then reconnecting it. If the issue persists, it may be a faulty control unit and will need to be replaced.