I hope some of you guys can help me as I've searched and searched but cant find any answers

Sometime last week the Concert stereo in my 2001 A6 stopped working and I've run out of ideas as to why. All the fuses in the fusebox are ok and the fuse on the back of the radio is also ok. The strange thing is if I unplug the stereo and pull the fuse then plug it all back in it magically comes back to life! Until I remove the key from the ignition for around 30 seconds, then it loses power again.

I've done some digging around and have found info on something called CANBUS which is what tells the stereo the ignition is on and powers up the radio? looking at the wiring diagrams on the radio itself shows the black connector should have 3 wires in it, but mine only has 2 there is nothing in the pin labeled K-BUS. I would like to think this is related to my problem and its an easy fix but I cant figure out why it just randomly started doing it for no reason

any help appreciated as its driving me mental! cheers