Look for a bleed valve somewhere on the pipes feeding the heating coil in your hot tank. It'll be at the top. Open it and check that water squirts freely. With the zone valve in the closed position, close the gate valve on the return pipe as well. Those gate valves don't always provide a perfect seal so some water may still come from your bleed valve.
Now for the important test. One way or another, get the zone valve into what should be the open position. Does water squirt freely from the bleed valve like it did before? If there's no change your zone valve never opened.
Now for the important test. One way or another, get the zone valve into what should be the open position. Does water squirt freely from the bleed valve like it did before? If there's no change your zone valve never opened.