The dreaded spray can issues.
As DMS says, make sure you shake the can for a good few minutes before using.
Also, never *start* your spray on a miniature. start the burst on a piece of paper, then start spraying the model.
Don't overspray- expect to cover the whole miniature in two or even three passes- don't hover over the figure waiting for it to turn completely black. If you're doing this, then likely you'll get too much paint on the figure. If the paint collects "Wet" on the miniature it will very often dry shiny.
Make sure you warm up the can before you use. No, not in the microwave, or on the radiator! If it's not stored in a warm room maybe just snuggle up next to it on the sofa and whisper sweet nothings
. But seriously, temperature has a big effect on spraying. The can needs to be room temperature.
Also the type of atmosphere you're spraying in has an effect. Is it damp outside (if you're spraying outside!). That too can have a negative effect on the way a can sprays. The best atmosphere is warm and dry- unfortunately of course, that means indoors, which is NOT recommended. Just remember that if it's a wet day you might be better off waiting for a drier one.
I know this from various problems I've had with army painter matte varnish.
Also, remember, when priming, the objective is to get the base coat to stick on to the miniature. It isn't to "paint" the whole figure black. I think most miniature painters over-prime (including myself).
) so maybe that's the problem. I'll give her a good snuggle later and get her in the mood, hopefully that'll help.