Hi Kyle,What game is it?Did you try another coil?Are the wires in the correct order soldered on that coil?Did you test the transistor after installing another one?

This is very odd...Lol! Post back if the problem returns

Yes that is correct the interlock switch kills all Hi-power to all the coils,The next thing to do is locate the transistor that runs that coil.The location of the transistor would be on the driver board in the backbox,The manual will tell you the location.That transistor will need to test with multimeter,Post back if you need more help.

Coils very very seldom go bad unless that coil is fried,Did you test the pre drive transistor?This transistor is the smaller one and the manual will tell you the location.
3 things to look into and test them again
1.The main Transistor
2.The Pre-drive transistor-smaller one
3.The Coil and diodes on that coil(If there are any)

Testing a coil,Power off the game.Set meter to ohms place one probe on the outer left tab hole of the coil and the other probe on the outer right tab hole of the coil.The meter should read 2 ohms or higher anything less would indicate the coil has/is shorted.