Heating the areas in question could work for sure. And its not the xylene you are smelling. Xylene is only used to extend the pot life and normally flashes of quickly
Polyaspartic is a humidity cure product and the colder the ambient temperature the slower the cure due to the amount of moisture cold air can handle. My guess would be that the areas in question are possible to thick and the top layer skinned over before the underlying material had time to cure...