I'm finally at the finish line! I tap the Purchase Ticket Now button at the bottom and... I get a form validation error: missing field. I double and triple check. THERE ARE NO OTHER FIELDS. I tap each field to make sure they indeed have values. They do. 12/
The S45 is rolling in to the station now. I decide to do a last second hail mary : I tap back, then select 24-Stunden-Karte because in this household we do NOT LOCALIZE the most important strings in the app. I quickly select BC, Adult fare, valid from Now, tap purchase, and... 13/
I have now paid, from my own Google Pay account, €10,60, for a 24 hour ticket that I will use for a single journey to the airport. I actually have no idea if this is a valid ticket for the S-Bahn, but I'm pretty far past caring at this point. At least I tried. /fin