Well re-connection did not work, so removed the drive again and this time removed the screws retaining the pcb to look for any burning etc. I was surprised that the PCB board contacts are made SIM style by pressure only, so cleaned these just in case, but still no joy.
Downloaded EXT2FS and still nothing, so turned the HDD over to my IT bud at work, who is a lot more skilled, and he has confirmed no response.
So that’s a pain, but hopefully the rest of the box is ok. Looking out there I don’t see a direct replacement drive for the Seagate ST31004242CS, so I would greatly appreciate a recommended alternative?