funny this, I've just had mine rejected several times with different cards too.
Also if you google sbb.ch and credit card, you get loads of results - all saying cards are blocked. The earliest I've found is 2013 on Trip Advisor.
So, the Swiss national train company cannot process card payments consistently for over 5 years - really?!
Shocking, disappointing and means that my son who is visiiting Switzerland for a field trip in June, will struggle with extremely expensive tickets as he won't be able to take advantage of the saver fares.
Have to say getting to Switzerland is a lot easier than travelling around it. And cheaper too.
Switzerland, you have dropped the ball badly.