Has anyone heard of non-oil pastels drying out?
It can happen.
Whatever the substance used as ‘binder’ for the pigments, things like temperature and humidity changes—even simple sunlight—can, over time, cause chemical changes that can work their ugly magic to degrade art materials.
Storing in air-tight storage containers or zip-lock bags can help extend the working life of such tools—not much help, admittedly, if your current batch has ‘gone south.’