Regarding the question, if I remember right, as I measured a lot of connections today, I don.t think it was any voltage between the input pins and ground, but I might be wrong. I.ll check tomorrow, if it helps.
If you have connected 12-24 v to the centre two terminal on the bob you should have about 7-12v on the input pins.

if you have not got any volts on the inputs pins then you might have burnt the pcb track out on the board. I have seen this in the past.

So just get one thing at a time working. Those bobs although cheap I find to be quite good.