The drive will have connections that say ENA or something along those lines, simply leave these disconnected.

If you have Mach3 DRO's are going around then you are getting pulses leaving the parallel port and if you are sure you have the right ports n pins set so those pulses get to the right places then you should get movement. Only something like the Enable stops them from working so leaving this disconnected usually enables the drives unless someone as changed the active state on the drives but without knowing more about the drives and the settings it's set too then can't help any further.

Obviously, you could have wiring issues or cable issues but again without seeing or being at the machine it's difficult to help.

It's worth re-installing mach3 and the parallel port driver just in case Mach3 as got corrupted which it does from time to time.