Yamaha DTXpress/DTXplorer/DTXtreme

This problem has cropped up before, but is usually because the modules default to a normal HH, even if you bought the Special kit.  You could try a factory reset (but you will lose all your custom settings) and then you would have to edit the trigger setting back to RHH.  I hope the HH Offset fixes it.  

It could be a faulty RHH, although it is fairly rare.  If you have a multimeter I can give you some things to check (resistances as you move the pedal) which would tell you if the pedal is working.

Keith.