Chinese firmware, Fons? 
So 1, the Zf with the Viltrox 16mm f/1.8 had set itself on MF.
2, updating the lens wth the latest firmware, after the latest Zf firmware update,
3, noticing the MF setting to AFS focus is allright with green confirmation box.
4, set to AFC focus but no green confirmation box.
Yes Chinese firmware.
Thank you.