It might not like its current diet, try switching it up. If you have made any recent changes in its terrarium, like taking out a rock, try switching them back.
Stress or sickness can cause these guys to quit eating. Also, make sure the tank temp is correct--that can prevent eating as well. Try different feeders as well.
Keep an eye on them and make sure they are eating. If too much time passes and they are not eating, there is a problem. They could be stressed or sick. You can try separating them or changing their diet.
Many leopard geckos suffer from internal parasites that they get from the crickets they eat. A vet can perscribe deworming medicine appropriate for your gecko.
