Rats! And I finally had something for you to try with the probing issue :(
When you say you "tried to reinstall the com port driver", do you mean you re-installed the plug-in (which won't alter the virtual COM port driver if already installed)? Or did you go into device manager and un-install the Virtual COM Port driver?
Does this PC have an internet connection? If so, Win10 may have installed updates "for" you that may be affecting the virtual COM port driver.
A couple of things to try:
(1) Power off the PMDX-424 and unplug the USB cable. Press and hold the push button on the PMDX-424 while turning power on. Continue to hold the button for 2 seconds then release. You should see a rapid flash on the green right-angle LED. Connect the USB cable. Wait 5 seconds. Try running Mach4. If you get a "The SmartBOB bootloader is running" warning message, then exit Mach4, power off the PMDX-424 and back on and try Mach4 again.
(2) If your answer above is that you did not go into device manager and un-install the virtual COM port driver (or you have not yet followed the FAQ link I am about to give you), then try the instructions here:
http://faq.pmdx.com/content/3/8/en/how-to-manually-install-the-virtual-com-port-driver-version-14.html(3) Do you have a 2nd PC somewhere on which you can install Mach4 and our plug-in? If so, try that and see if Mach4 is able to communicate with the PMDX-424.
Bob