I have same problem with my rabbit before when I adopted him.
He didn’t eat hay at all. He was on fiesta diet (I know it’s bad) and he refused to drink water. I tried so hard.. so hard.. very hard.. to make him EAT HAY!
I tried my last solution which was a great success, I stopped providing pellets in the mornings. He will have nothing etc to eat except hay next to him until at nights he will get less than 1/4 cup of vegetables (that’s way less than we are suppose to feed rabbits). He couldn’t handle to be hungry and ate hay right away. I slowly increase amount of vegetables everyday and I switched fiesta pellets to oxbow pellets. He still kept eating hay like there’s no tomorrow.
(don’t follow this method if your rabbit don’t eat any food for more than 12 hours)
That was happening in about 4 years ago. He is five years old right now and still love to eat hay (Timothy, Orchard, and Oat) with more than 3 cups of vegetables a day.
*Talking to myself* Wow, it’s been four years since I had my rabbit came into my life. Felt like I had him a week ago -_-