Update, I have plugged the high hat foot cable and plugged it into the kick, where it does make a sound when pressed. However the high hat cymbal still does not make a sound even when the cable is switched with the ride.

OK.

So.

Plug the hi-hat pad into, say, the crash input. Does that work?

Plug the crash pad into the hi hat pad input?

(can I also check - not being patronising - the hat pedal is in the hat pedal input and not the hat pad input, and vice-versa...)

Problem occur on all drum kits?