Post a link to this ebay cable.
Odds are if you 'uninstal' a USB driver, then plug the USB in, Windows will automatically find the correct driver and install it. (I'm thinking you know all this already)
It's a good bet the reason you can't do anything are the setting in the program. You probably have to set up the 'baud rate' and/or cable/interface type. Something in the options screen?
I looked at the free version. Didn't find anything I can advise you change.
Just caught that you're in England. I wouldn't doubt is US scan tools won't work for you. Not sure but I'd see what others in your country are using on the cheap.