If you grounded that transistor and it’s not firing I would do a continuity test on the traces . I would make sure they are getting to the pins on the connector . You said you built a new harness . Make sure it’s pinned correctly and also getting continuity . If all is well then I would replace that transistor and see what happens . Sttng is a game that is crazy to get dialed in due to all the optics and diverters involved , plus those cannons moving with old wires , but once it’s done it’s an awesome game .