MK4 is not found after upgrade to V28
 

I had an old version of MK4 software.
I have burned a V28 disc and insterted it in the MK4.
After a while the screen went blank for a long period.
I restarted my car and I got a changed screen (light blue) like an MK3.
On my screen, the Navigation menu is now vanished.
The power led of my MK4 is also down.

Can I do something to restore my Nav ?

Yes, you can. This happend to me as well. You will have to down or upgrade to get the software to rectify.

Most likely reason for the the fault is that the picture modification to the navboot was not done properly.