He might just be so used to dubia roaches, that that is what he prefers. A beardie won't starve himself so keep offering the crickets and he will eat them when he is hungry enough. They get used to being spoiled and can be a bit stubborn when change occurs. If you have a tongs, maybe try and see if you can hold the cricket in front of him and see if he takes it. If not, just keep offering them. He will eat them sooner or later!