OK, got it fixed.
Not sure if this will work in every case, but did in mine, or this case.
Open the Plugin Control and Activation box where you configure your plugins.
Click on the CONFIG tab to the right of your XBox you want to set up.
When that box opens, you will see a place to enter a Vendor ID and a Product ID.
If these are filled in, you would, or should be OK. If they only have "0" in the boxes, you will to enter something.
I used some # I found on a web site and it started working after I restarted Mach3.
Don't know if it will work for all controllers, or not, but here they are
Vendor ID: 0E6F
Product ID: 011F
Like I said before, don't if it will work in all cases, but did for me.
Good luck, and thanks