What is the rest of his diet like? You may need to lower the amounts of some stuff so that he will be hungry enough to eat the hay. He HAS to eat it, so don’t feel bad if you have to cut down on other stuff that he likes more.

It is true that some bunnies don’t particularly like hay. My Spockie ate it absolutely last of any choice of food, and he never ate a lot. I worried and frequently tried different hays, but he never got a strong taste for it.
But it is better to cut back the other types of foods to get your bunny to eat more of the hay. Pick the kind he seems to like most of the ones you’ve tried, and feed him that. You can also put it into his litter pan on the side so he is tempted to eat it while he sits there. Also, if you put the hay in his pellet dish, he may munch as he forages through the hay to get to the pellets. There are also some natural products in the store or on the Busy Bunny website store that are meant to mix with hay to make it more appealing. They use dried flowers and herbs that are edible and appealing to bunnies.