I must have done it wrong - or it may have been that we couldn't get the last train after the match - oh well too late to change it now
Someone was saying to me that you can't get the 50% discount on the website, you need to use the app. This was after I'd already got the 50% discount from Geneva Airport to Sion.
Anyway, what he told me seems to be true of certain journeys (he's travelling from Zurich).
So, if anybody else is having trouble getting the discount try using the app.