The most common issue is that cards are not accepted if they lack the 3d-Secure feature. I think it is easiest if you just try. Worst case it simply won’t work. (Don’t be confused from the error message saying that your payment institue denied the payment!). If you find that none of your cards work, most offers (namely, all offers which are not safer’s offers or supersaver’s tickets) are exactly as cheap if bought with cash from a ticket machine upon arriving in Switzerland. At least in big stations (like the ones at major border stations and airports), there are ticket machines and in most cases even staffed counters where you can also buy your ticket in the worst case.