Hello tianshi
Did you buy both of your tickets with login? Please make sure to refresh the page of your tickets in your mobile App and try to log off and login again.
You can also open the E-Mail with your ticket on your mobile and show the PDF-Form during your travel.
If the problem persists, we recommend contacting directly the SBB Online-Support: ticketshop@sbb.ch.
Greetings,
ValerieS