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.
Don't "think outside the box".
There is no box.
Do it correct, or do it twice.