Perhaps you're not getting water into the unit. Down at the back where your water line comes in, there will be a solenoid. This is a valve that, when energized, lets water through. The head sends voltage down to this device at the appropriate time in the dump cycle for exactly the right length of time. This device works on line voltage so you could remove the wires going to it and hook them up momentarily to 120VAC.
If you get no water flowing into the ice maker tray you either need a new solenoid, or ice is blocking the path of water to flow through the back wall of the freezer into the icemaker tray, in which case a blow hair dryer will come in handy.
If you get water, perhaps it's wiring, or a faulty new head, (I've had several). Also, remember if the lever is in the up position the unit is turned off. And, the ice maker has to be frozen to start working, (you have to leave it in the on position for a few hours before you get any action).
Actually, because air might be in the lines depending on how long it was off for, leave it for a day or so. You may find it starts working on it?s own. Hope this helps.