You will also need to check if the mach3 configuration and the wiring. Since you tested the connection from the motors to the drivers, the connection from the computer to the interface may still be the issue. It could also be the connection from the interface to the drivers, but we test all of these units going out, so I don't believe that would be the problem.
If you have a redfly that uses a parallel cable, you may need to check to make sure the parallel cable is functioning properly, and also, make sure that the interface is also powered using a usb cable.
If you have a usb interface (the terminals will be labeled XD, XP and so on), then there may be a wire not seated correctly in a terminal.
Click the link to respond:
I plug in my redFly for the first time and after configuring Mach3 and rechecked my settings axes Y and Z are working well, but X is not working, just for testing I plugged in each motor to the Y and Z and they work fine, but no motor works when plug into the X axes of the redFly, also one of the NEMA 24 425 Oz motors dose not turn just jitters.