what style of BV do you have in your machine? is it a DBV, MEI, WBA, JCM?
if it is a DBV200 those always have power issues, if it is one of those you can jiggle the power wires on the left side of the bv(2 wire red/black if i recall right) and see if you can get it to cycle.
if you know you have power to the validator you could try the option below.
sometimes with the other validators i have pulled them out and did a netplex where the machine confirms it doesnt have a validator, then put it back in and re-netplex it.