Berliner Sparkasse Onlinebanking FAQ:

Why do I get the message ‘mobile device, can’t perform smsTAN money transfer’ when using my Desktop computer.

A possible cause is the display resolution. Your computer is being detected as a mobile device by our online banking system. smsTAN is not working from a mobile device.

Solution: Change the display resolution

So 1920x1080 does work, but 1080x1920 doesn’t.