I have had similar issues with features that have stopped working. I think one was that I was unable to change motor settings. The only solution I found was to save the setup files (.XML extension) and reinstall Mach3. The safest way to try this is rename the Mach3 folder something like Mach3old then install a new Mach3 load into a folder called Mach3 then copy over the XML files, gcode, addons and licence file (and possibly other stuff that will show up when you look for them) from Mach3old to Mach3. If this fails to fix things you still have everything as it was in the Mach3old folder to fall back on.
