Everybody hold on there, we are getting confused. Green is Forward. Blue is Reverse.
Per your testing so far, showing no voltage on the green wire in the junction box, that is pretty good evidence that the switch is bad. But not absolute evidence. The wire could be broken somewhere along the line. Or it could be shorted to ground in the motor, but that ought to blow a fuse if it is. One more time, no voltage on green would mean no forward gear. Original problem said no reverse.
Just saying, try the 12V to both blue and green (SEPARATELY) at the motor to verify that it is OK, then proceed with the switch theory.
BTW, what horsepower is this motor anyway? It matters when trying to find the wires at the motor.