It appears that you don't have a genuine Copy of Mach3, is the UC100 genuine brought from the manufacture or there reseller's if the UC100 is genuine then it will not work correct with the Chinese copy of Mach3
Looking at the settings you posted, the Step / Low would normally be red X you would also have to change the way it Homes as well
In the General Config Page look at the active Plane Movement this should be X-Y
Distance Mode Absolute