It would help to know what you are feeding him and what he will eat. Be specific with the brand of pellet, type of hay and what veggies you have tried.
Some rabbits eat more hay than others and some prefer pellets or even veggies. Each rabbit is different, so you can't base what one rabbit may eat as what your rabbit should eat.
Keep offering him hay and veggies. Limit the pellets so he can't be eating them all day. Hopefully, if he is hungry enough and the hay is there, he should eat it.
You can try hiding the pellets in the hay. Make a pile of hay and sprinkle the pellets in it. Getting him to see you do it can help so he knows they are there. While looking for and eating the pellets, he may eat some hay and discover that it is good.
Try different veggies and hay. Some just don't like certain ones, but will eat others. If you feed timothy hay, try brome, orchard grass or even a bit of alfalfa. For veggies, try ones that smell good, but only give a small amount at a time.
Exercise could help. He may be more willing to eat other foods when he is tired from running around. This could also help with the cage chewing. Giving him toys in the cage can help too.
A vet check would be a good idea as well. There is a difference between won't eat hay and can't eat hay. He could have some dental issues that you can't see.
Be persistent. If you give in by giving him more pellets, he won't have to eat the hay. Give a set amount of pellets per day and that is all he gets. If he eats them all at once, that is his problem and he can eat hay if he wants.