After tens of minutes of faffing about trying to work out why the shift key on the keyboard on our Medion PC stopped working, I traced it to … a keyboard reset (aka take the batteries out, put them in, re-sync the keyboard with receiver). A good reminder about basic fault finding – isolate the issue as much as possible. It was some while before I plugged another keyboard in, having started with drivers. So, if you have a cordless or wireless keyboard, try the batteries early!
And, this post written so others can find it via searches when they have the same issue!