Sometimes they will get bored of a certain food, usually (at least of what I have heard) if you do not offer that certain food for a few days or longer if needed and then offer it again they will eat it. Give it a try, if not maybe try a different type of live feeder. There are many types of worms and dubia are amazing.
Oh, another thing, what is his set-up like? Like temps, height of basking spot and distance from light.
Sometimes it could also be due to temperatures or maybe he has parasites effecting his health.