Quoted from RVApinballer:
Sounds like you might have fried the transistor by wiring it backwards and it's now shorted? Just a guess, but I'd test the transistor that corresponds to the garage coil. There's videos on YouTube on how to test whitestar transistors on LOTR for example and the TSPP manual can tell you which Q # is the one. Pulling driver board is easy on TSPP
Yep you blew the transistor. It really is easy to fix if you have basic soldering skill and take your time.