Here is the update. Still dead in the water after reflashing the same USB drive which seems fine from a windows PC. I copied the whole config file from the drive before flashing and added a few files back on to it after: the shares folder, pools folder, basic.key, disk.cfg, ident.cfg and super.dat.
I have a black screen with a flashing white cursor int he left hand corner. Picture attached.
UNRAIDSTUCKATFLASHING CURSURmp4.mp4