Head Unit not starting up

My head unit (central screen) is completely black and not responding at all. The screen between dials on instrument panel is however, fine.

Have I bricked the head unit, or does it just need a re-code?

I did take it out, as needed to clean the space behind it. Not wanting it to dangle, I did disconnect it.

Recently changed the battery, but that was weeks ago, and didn't cause any problems.

I've found that the cabin filter only has foam on two sides, not four, so dirt was taking the easy route instead of going *through* the filter 🙄

I have ODBII, or would i need VCDS?