Rabbits are funny about hay. My first rabbit Sony didnt much care for it, and when I took her out into my yard with me, she focussed on things that werent grass/hay, like dandelions, violet, or plantain. She did like any leafy vegetable, like kale, collards, turnip greens, mustard greens, broccoli rabe; and also liked carrots and most fruit: apple, pear, peach, nectarine, plum, apricot, grape, cherry, banana. She recoiled the one time I offered her a big strawberry, and I never offered her any citrus fruit. Fruit is high in sugar, though, and I dont know if it would be good for a rabbit in large quantities. I usually give my rabbits no more than the equivalent of a tablespoon or so of fruit at one time.
My two boys, Hans and Franz, are easy to please. They like anything I listed for Sony above, plus timothy or orchard grass hay. They like white clover, red top, orchard grass, or fescue from my yard (or hay I make myself from any of those). But again, if I offer them dandelions or anything else at the same time as the grass or hay, they eat that first and go for the hay/grass last.
My rabbits havent cared much for summer or winter squash when I offered it to them. Also, I think alfalfa hay is too high in certain minerals to be good for rabbits as a main food, although they can eat it as a treat if they like it. Ground alfalfa is a main ingredient in the pellets I give my rabbits.
I think the approach Chelsea sugests above is good- keep offering him things which are good for him. I suppose it would be best to initially buy things that you like too so they won;t go to waste. But my rabbits are at the point where they crowd around my feet whenever I have something in my hands that looks like food.
Peasant (1963-1972) and Fluffy (1970s?-1982- I think of you as 'Ambrose' now)- Your spirits outshone some humans I have known. Be happy forever.