KARNAK 19 Flashing Cement or KARNAK 19 Ultra Rubberized Flashing Cement begins to skin-over after application. Depending on the outside temperature and the thickness of the application, full curing(Drying) can take from a few weeks to months.
Based on your email, where and how was the material applied? Photos would be helpful as well.
You can contact me at KARNAK at mgada@karnakcorp.com or phone: 8005-527-6251.