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A successful payment is always completed by a payment confirmation e-mail. Does the screenshot include a QR code and a ticket number (please do not post it here)?
If you want to be sure that everything is alright, you can call the SBB Contact Center: +41 51 225 78 56 (24/7, waiting times may occur), or see any SBB travel office on the day of arrival. Should the Swiss Half Fare Card purchase not have been successful, you could still buy it on-site upon arrival. You are not required to be in possession of the Swiss Half Fare Card for buying reduced (half fare) tickets in advance. Whether you are eligible to use half fare tickets is checked by the ticket examiner only, not before.