Hello Niongenet15
Can you please also check into your account on swisspass.ch (and not only in the SBB app)? The invoice should be visible under Invoices.
If you cannot log in, please contact us by phone at 0848 44 66 88 (CHF 0.08/min), via live-chat or ask at any SBB counter. Here our opening hours.
I wish you a lovely day,
Chiara_S