That's interesting because there IS some sort of response. The drive spins up the moment the USB cable is connected, but I cannot hear the familiar connection sound. It does suggest a possibility there may be a problem with the cable.
I do not have second cable to test, but I have now found someone with a USB3-enabled PC. It will take a couple of days maybe but they can try the drive, together with its cable.
Before that, I'll try holding the connectors more firmly in place to see if I can get a better response.
Appreciate your reply.