On my Samsung it works fine so I cannot really help but I mostly want to stress that expecting last-minute availability on Nightjet services is risky to say the least. You should book it as soon as your dates are set (so at home with your PC).

Otherwise try https://shop.oebbtickets.at/en/ticket → it might work better.

Yes of course, in any case it feels strange you can’t use it on an iphone or ipad at all. The app works great but it doesn’t have nightjet tickets. 

The ÖBB app surely sells Nightjet tickets and pass reservations.

If the app shows the “ticket not available” message the option is usually just sold out. But I can confirm that the ÖBB app does sell NJ tickets and pass reservations. Just keep in mind to select that you want “one-way tickets and day-tickets” and not only a seat reservation since technically you’re looking for a pass supplement which includes the reservation, not just a reservation.

Yeah, you are right! Thanks!

The ones I tried on the app happened to be sold out. When I first made sure there are seats and looked it up in the app, they were available. 

Sorry for this non-existing problem. Anyway if you have iPhone, download the app .