Hello Yureegi65
In the contrary to the resident Half Fare Card, the Swiss Half Fare Card is in fact just a normal ticket that proves that you are eligible to purchase tickets at half fare. It does not automatically activate the half fare setting in your SBB Mobile App, whatsoever.
You have to do that manually for each passenger having the Swiss Half Fare Card and before you purchase tickets for the first time. How? Read my answer here, I explained it with screenshots:
https://community.sbb-tickets.cc/d/26418-how-can-i-save-the-info-of-swiss-half-fare-card/2
Still not a no brainer?
Kind regards,
Roland