Getting closer (I think).
Cleaned the device and now it seems to work. Wired it up to the the mill for a test(not installed). The green light on the hardware page responds with on and off. The same does the red status LED on the BOB (G11G Multifunction CNC board Rev. 9 from CNC4pc).- but Mach3 vil not show the REW, the display just flicks wildly even if no a speed is called for.
For ref. my setup is: Windows 10, Mach3, Smooth Stepper ver. 1.2, BOB as above and the mill is a SIEG KX3 CNC Mill