I am new to crested geckos too, and could barely notice if my little guy was eating at first or not. The solution for me was to see that he was still pooping. If he doesn't eat, there won't be any stool. In my case the guy didn't eat much for 3-4 days, then started eating fine. He also prefers mealworms, but I rotate crickets and always give him CGD as well. Good luck.