Mercedes Sprinter Microphone Problem

That sounds like a faulty infotainment system module. Can you still use voice recognition for other things, like media controls, or is all audio input dead? Does the volume control still work?

Volume control still works, but speech recognition is completely dead. So you think it's definitely the infotainment?

It sounds like it. If speech recognition is also gone, it's almost certainly a defective infotainment system module. A workshop visit is unavoidable. It'll probably be around 815€ for the microphone fix.

Thanks for confirming my fears. I took it to the shop, and you were right. A new infotainment system module fixed it. Costly microphone fix though.