Product review (1 stars): Often replacing parts like the solenoid or sensor will put things back in ...
First solenoid valve replacement leaked.  Made in Mexico, the simple fact was that the diameter of the orifice that accepts the locking tank drain (which is rubber coated to seal in this orifice) was not the correct diameter.  Before you install a replacement valve, take the new valve and lock it onto the water tank.  Fill the water tank and observe for leaks before you take the time to install the valve in the humidifier (which is one of the least-reliable products ever made by Honeywell).

When working perfectly, which is rare, the product works reasonably well if you have near-molecular-pure water.  Often replacing parts like the solenoid or sensor will put things back in working order - at a cost.

Honeywell should offer a full refund everyone who purchased this unit.