Just a quick tip to fix this baffling problem; put on your Sigma Art lens on your Nikon body (in my case a D500) and the autofocus doesn’t work (!) – if you look at the lcd the autofocus sign will flicker…dafuq?
Well the solution is simple; pull out the battery and put it back in again.
What the hell is going on? – I don’t know but the trick works.
And oh btw, here’s an image I took yesterday;