I thought some of the Mach3 users might of commented by now, as it's been a few years since I've had much real dealings with it.

I'm guessing you're needing to home the machine, however it's not clear if your machine is setup to use home switches.

It's probably best to post over on the Mach support forum - http://www.machsupport.com/forum/index.php
However, people will need some details about the machine.