Can you verify there is 120v to each coil? Perhaps the coils are faulty...
both coils going bad at the same time is possible, but more likely is a broken circuit between the Jones plug & carrier switch on the bottle stack, the coils (coin reject electromagnets or C.R.E.M's for short) are powered by 120 volts so there is no transformer to worry about.
unplug the coinmech & check for voltage between the coinmechs female socket, pins #6 & #2 if there is 120 volts between the two pins then everything's OK from the bottle stacks carrier switch, (this switch also controls the "Have a Coke" light on many Cavaliers) some times when people attempt to repair or rewire the "Have a Coke" lights ciruit, they accidentally reverse the two connections on the switch & when this happens the Have a Coke light stays on all of the time & the coinmech will reject all coins
the CREMS are also controlled by the change tubes empty switch, which should light up the "Correct change only" light, so if you have no nickles in the tubes ( or just not enough of them) or the tube switch is stuck, this will also cause the coinmech to reject coins
my guess is the bottle stacks carrier switch is stuck or a bottle gate is stuck & didn't reset the stacks mechanism that controls the switch, or the little return spring for the carriers stack switches "toggle plate" is broken & it's stuck in the wrong position.
take a look at the bottom of the stack.