It's uncommon to find a gecko that accepts pelleted foods once they've grown accustomed to more natural forms of food. I once purchased a container of dry pellets that were apparently being sold as gecko food only because it was marked down to a dollar and looked like it would work well as a cheap food for some of my inverts.
You could try using caterpillars or other organisms with softer exoskeletons and higher moisture content than a superworm or mealworm. They may accept the pupae, though.