What is the error?
Please kindly note, for security reasons, your credit cards must support 3D secure ID to purchase tickets through the SBB websho (sbb.ch)
You can also purchase the Swiss Travel Pass from Switzerland Travel Centre (a joint-venture of Switzerland tourism organisation and SBB), the official point of sales for tourist tickets such as Swiss Travel Pass. The cost is the same, so is the ticket identical. The stc webshop is not as restrictive the SBB one: Swiss Travel Pass | stc
May I kindly inform you that the Swiss Travel Pass requires your physical passports on the train upon ticket check. Without your physical passport or national ID card, the Swiss Travel Pass is not valid.