I'm definitely not a good source for answers on this, but it sounds to me like you have an issue with an interlock...possibly the front door on the spindle. That knob/latch thing kept giving me grief, so I bypassed the switch and have a bungy cord holding the door closed. I'm pretty sure mach3 needs to see all the safety switches closed before it can even look at the drivers. I just turned it on, disconnected the communication cable to the Z axis and mach3 reset like normal. I did a "home all" and it showed the Z axis moving on mach's display, but the machine did not physically move. It did not cause a flashing reset button on the screen.
Hopefully, someone else will chime in with better help.
-Mike