Rabbits are so fussy with hay! There are a few alternatives you can try.
1) try mixing in two or three types of hay. Rabbits love to 'choose' which hay they prefer according to smell and taste
2) try spraying a little apple juice or pineapple juice on the hay to add a sweetened flavour. Rabbits like us humans, love sweet things!
3) refresh the hay multiple times a day. Rabbits can differentiate between 'old' and 'fresh' food
4) add a small amount of hay in your hay feeder or wherever you place the hay and if it becomes less and less, then that's a good indicator that your rabbit is munching on them. You won't be able to tell if you provide your rabbit a whole bunch of hay.
5) remove any fruits or vegetables that is in the sight of your rabbit and allow your rabbit to only have pellets and hay in its surroundings. This will leave your rabbit no choice but to eat what is in front of them as this will leave them thinking "okay well I guess I won't be getting any greens or fruits, better eat what I have!".
If none of those alternatives work, then perhaps your rabbit is in the first phase of experiencing dental problems. When my rabbit was refusing his hay, I tried all of the above and none seemed to work and that was because he had spikes and Spurs (this was found out by my rabbit doctor when she examined him). Ever since he had his surgery, he's been eating his hay again
. When rabbits have dental problems, they'll avoid foods that are solid and especially hay because hay requires a different chewing motion than do other foods.
Let us know how your rabbit goes!
Hope this helped