If the solenoid is making a continuous noise (meaning it is being powered), then there is a problem with the control board, because the solenoid should only be powered momentarily to release the dispenser latch. Does your dispenser lid open immediately when you start a wash cycle? However, if the CB has a problem and is sending power to the solenoid continuously, then it has likely burnt out/damaged the solenoid and so both could now be bad, but the root cause is likely the CB.

If the problem was a faulty solenoid, then it just wouldn't open the latch, but I don't think you would get a constant noise. This is the problem I am having (my soap dispenser won't open) even though it is a relatively new washer. I have been trying to locate a replacement solenoid, but it seems you have to purchase an entirely new dispenser. Does anybody know if/where you can obtain just a solenoid?