Dear @TimTom
Have you tried logging out and in again? Or maybe deleting the app and downloading it anew? This way you’ll have the newest version – usually this solves most problems and bugs.
If after this, the app still does not work, I suggest you contact our specialists per mail at ticketshop@sbb.ch or per phone calling this number: 0848 44 66 88.
I wish you a nice afternoon!
EleonoraS