Hello, check to see if you are getting 24 volts to the solenoid valve, if you are and it does not click on to let the water into the humidifier then the solenoid must be replaced. However if you are not getting 24 volts to the solenoid valve check if yuou are getting 24 volts at the transformer, if not then turn power off to transformer and check the continuity of the secondary side of the transfomer, you should have resistance if not replace the transformer. if that checks out good check the wire connection between transformer and solenoid and make sure it is tight. If wire connection looks good then either humidistat is bad or current sensing relay/sail switch.