I had the same problem last Sunday ( Sept 24, 2017) I had Nikon D5300 and the AF-P 18-55 lens suddenly stopped auto focusing. I have tried several methods as suggested above but t was still not working. I have tried a different lens and the auto focus is perfect. Hence, I am now confirmed that there is some issue with the lens. When I am changing the setting to manual the shutter is firing but still there is focus issues.
I am still struggling . Someone plese help?