Rottendog have a lifetime warranty as far as I am aware. Contact their support and the guys will help you.

Hmm, this is strange..If you grounded the transistor and it fired, that means the coil, transistor and wiring is ok. That only leaves the board itself.....perhaps you need to go back and look at the board, you may have another component on it that maybe bad. I'm a fan of Rottendog myself...I had a couple of friends who had problems after installing but almost always it turned out to be something else (connectors, ribbon cable etc).

Unless they are different on the RD boards grounding the tab doesn't actually test the transistor it just tests the coil, wiring, etc. I would venture a guess that the drive transistor or pre-driver is bad.

Oh okay, but If the transistor is shorted or bad wouldn't the coil be locked on?

Shorted yes it would lock on a coil but a transistor can fail open as well.

I'm sorry but I'm not familiar with their boards and don't know what transistor types they use in the game but it should be a NPN and the tab should be the emitter. With that in mind and the game off if you put a meter in diode test, black lead on the tab and the red lead on each leg you should have a forward voltage drop of about .8-1.2V from the base to the emitter and a very high reading from collector to emitter (one leg will be a dead short to the tab as they are electrically connected). I'd suspect you won't see the base to emitter drop and it will be open indicating a bad transistor. Also If you have a logic probe you could probe the base of the transistor (just be careful and don't put the probe on the high-voltage legs of the transistor, could seriously damage it) while the game is in solenoid test mode and see if it cycles, if it does the pre-driver is working and the driver transistor is bad, if not the problem is the pre-driver or further up the logic chain of the board. You'd have to follow that back up the chain with the logic probe if that's the case.