Quickly browsing the web, it seems what is supposed to happen is that the printer and phone should establish a wifi-direct connection with each other.
Do you have Wifi turned on (not sure if it should be necessary but worth trying) ?
Hi CH and thanks for your support.
Yes, the ZF6 and printer do connect (even) via wifi-direct but this is not the way I want to do it (and it doesn't need the near field communication).
Previously, I always connected my ZenFone 2 to the printer via NFC and I could print every kind of photo or document.
By now the ZF6 and printer connect via NFC (Brother app establishes the communication) but the print command doesn't work.
Maybe it could be a firmware or driver problem (of ZF6 or Brother)?