Pocket Cinema 6k Black Screen

I have updated to version 6.6 and at the end I have been left with the black screen, it has died, it does nothing and the software update no longer recognizes it

Don't worry, it's not dead.

When PCC4K/PCC6K firmware update fails:

Remove all power source to shut down camera (remove the battery too).
Ensure that it is indeed powered off (fan is not running).
Connect power and then switch the camera on WHILE holding the focus button for a few seconds. Camera should now come on with fan running but with screen blank.
Connect to your computer and see if you can re-run the updater.