You've confirmed your driver board is making 50 volts. Now make sure that voltage is getting to the coils.
Balls removed, game in switch edges test, coin door closed, playfield raised all the way. Black lead on the ground braid in the cab, red lead to all the coil lugs other than flipper coils.
Lockbar and side rails are also grounds. Be very careful about not getting 50 volts where it shouldn't go.