Fultondale, AL
You need to use a meter to troubleshoot this. Check the resistance of the coil. You should see a low ohm reading. If the coil is good, measure for dc voltage at the coil. If the coil is good and there is voltage at the coil, you should be able to ground the tab on the transistor and the coil should fire.
Also, these type coils do not have a plunger, they just pull in a plate. If the plate is too far away from the magnet, it may not pull in. I'm sure you checked for the obvious like the linkage from the solenoid to the gate being disconnected?
