What primer did you use over the powdercoat?
And, what paint are you now using?
Was the can VERY adequately shaken?
And is the temperature of both the frame and the room where you are spraying warm enough - and staying warm after painting?
Have you tested the paint on something else, placed in the exact same conditions recently?
What is the humidity in your painting environment?
Does not sound like an issue with the powdercoat at all. You should even be able to spray paint over a plastic soda bottle or a chrome bumper if the preperation is correct, the paint is appropriate for the application, and instructions for the paint are all followed ... Could be just a bad paint can or the primer you had selected is incompatible with the paint you are using.
Adequate and consistent temperature makes a big difference. Don't expect things to work right if you are leaving the bike in an unheated garage in December in Minnesota. 70 degree room temperature is usually fine. And, typical household humidity range is also usually good too. Just be sure to read the specific instructions in tiny print on the can. And, don't leave the frame in front of a furnace blowing out dust onto the project or heating everything unevenly.
Winter sucks. I really will not be able to paint anything for several months.