Hello jjuanangarcia
Hello first as we like some niceties over here 🙂
when I try to buy a ticket
You mean a class upgrade or a ticket for a route that is not fully covered by the GA? Why else would you need a ticket?
I go to the last step to select ticket and it appears the full price.
The GA summer offer is not automatically taken into account.
You have to set the discount type in the passenger details to GA 2nd class or GA 1st class, what ever GA type you hold. Do not forget to undo the setting after the trial period has ended.
See the screeshots in this post, simply do the same for the GA:
https://community.sbb.ch/d/26418-how-can-i-save-the-info-of-swiss-half-fare-card/2
Kind regards,
Roland