SIUDI6C - need to unplug and re-plug

[PianoManDan]

For a number of years I've used the SIUDI 6C interface with Easy Stand Alone (my dmx fixtures have been basic, so this has been fine for my needs - creating scenes etc.)
A recent change in lights has prompted a re-think with software, and Sunlite seems to be the better option as it will give me some pre-programmed buttons ideal for live use on my touchscreen.

However, I can't get any action from my DMX Interface.
On launching Sunlite 2002, the software will detect the interface, but then the Green LED will not flash, and will not control the lights. If I change the DMX Values, nothing happens. I can then unplug the dmx interface, and plug back in, and the lights will update with the latest DMX Values - but then fails to respond to any change in values again. Unplug and re-plug will update the lights again, but still no actual live use.

I have installed Daslight Virtual Controller version 1 (the only version SIUDI 6C will work with), and I get the same problem.

Any ideas whats going on?

If it helps to shine any light on the subject, I get a similar problem with ESA too, only unplugging and re-plugging once will make it work without any further problems (Green LED Flashes as it should, and all dmx values update live).
I've uninstalled an reinstalled the DMX Interface, completely deleting existing drivers, and reinstalled using the most up-to-date drivers available.

Any help would be greatly appreciated.