What do I do if I have bought a ticket online but my mobile phone doesn't work at the ticket inspection?

Ordered mobile phone tickets are displayed directly on the smartphone or tablet after completion of the order process and cannot be printed out. The customer must ensure that the mobile phone ticket is displayed correctly and legibly on the smartphone or tablet and can be checked together with the photo ID provided during a ticket inspection. The customer is responsible for the existence of a valid internet connection and a sufficient power supply in accordance with the GTCs.