There are some days when technology just doesn't want to play ball. And in my experience 99% of these days are when you're on a developer training course and its the exercise/labs machine that's being difficult. I had this recently on the XM Cloud developer intro course. I've no idea if anyone else would ever see this issue (or how it was caused) but it didn't return much useful info in Google, and I did find a way to fix for my problem. So it's documentation time...