Check the output voltage of your LPT Parallel Port. Measure the voltage on an axis Direction Pin – it should be approx. 5V when you jog that axis in one direction and approx. 0V when you jog in the other direction. If the voltage only gets to approx. 3.3V then that could be your problem.
The PC running Mach3 should be regarded as a 'Machine Controller' and not connected to the Internet or a network. Doing so will result in problems sooner or later.
Avoid any Chinese motion control systems. Not only do they not have any manufacturers support they lack functions that you may later require.
Probably the best way forward, considering you may wish to change to using Mach4 at some later date, is to consider the Warp9TD ESS motion controller together with the Gecko G540 stepper controller.
OK, they are not cheap but if you want reliability, support, quality and a system that is to a large extent ‘future proof’ that, in my opinion, is the way to go.
Tweakie.