Get the kind of hay that has more stem, longer and big stem. My buns eats those hay, i.e., the loose and smaller grass type hay bundle that you show in your photo. But they eat a lot more when the hay is long and the stem is big.
Now, w/ those long stem hay, I can tell they won't fit in the bag that you have in your photo. The farm hay in bale would be that big, and is much, much more healthier for their teeth.
When my buns eat those hay, they can't get enough of them, but when they eat those tiny hay (the ones you have), they only eat them when they need to.
Look at the top right corner of this photo, you can tell those stem of the hay is longer, bigger. Rabbits love those a lot more than the small bag hay.
This may be partly the reason your bun is not eating the hay. A rabbit's diet should be 90% hay.
Besides, a bale of hay is cheaper than that bag of hay of yours. The entire 65 lb. bale of hay is only $5. And it last 1 year, enough for 2 buns