Hello Vicky51
You are talking about the Swiss Travel Pass. The SwissPass is for residents and you should not mix up the two.
Jungfraujoch tickets with Swiss Travel Pass are not available through SBB.
Discounted Jungfraujoch online tickets can solely be purchased with Jungfrau Railways, as a ticket with a 25% discount is only available with them. Or, at any station with a travel center.
See here:
https://www.jungfrau.ch/en-gb/jungfraujoch-top-of-europe/buy-jungfraujoch-ticket/
However, we strongly advise not purchasing mountain excursion tickets in advance; the weather plays a major role in our country, and it can well be that on the day of travel, the weather is bad, and you will end up in clouds with zero views.
For other excursions, where the Swiss Travel Pass grants 50% off, or for class upgrade tickets, for which the Swiss Travel Pass allows purchasing them at half fare (½), you can change the reduction card settings in your SBB Mobile App to reflect half fare. How is this done? I described it here; it works the same as for the Swiss Half Fare Card:
https://community.sbb.ch/d/26418-how-can-i-save-the-info-of-swiss-half-fare-card
Kind regards,
Roland