Suzy, I was frustrated too with SN7pro and had to rely on skysafari, updating often to get my shot of 252P. Bit of a let down, I do like SN and generally find it very reliable for me. It did come up with another comet nearby which I was going to try for, but a bit more research it had broken up after its last swing past the sun so its magnitude was beyond my reach but SN still had its pre-breakup data
SkySafari proved to have it accurately plotted and helped me line up my DSLR and 252P was dead easy to spot in my first test shot, always a good thing.