My rabbit was like this! Due to pet store owners persuading rabbit owners that the 'grain pellet mix' is essential to a rabbits diet and is "very healthy", I've been buying this type for my rabbit for two years! (He's a dwarf lop. 2 years old). Until recently he developed spikes and I was told by the rabbit doctor to discontinue this pellet mix and buy oxbow pellets (and yes he had his dental surgery to file the pointy teeth, and also, the spikes were not because of the pellet mix). Anyway, I purchased the oxbow pellets and slowly transitioned it to him but he would absolutely refuse it no matter the cost! Even if I were to remove his treats and vegetables and only have pellets and hay in this cage, he would still refuse. BUT! What I've been noticing about him eating the grain pellet mix over the two years was that he would repeadtly tip over his food bowl, almost as though he was searching for a particular pellet. So what I did was, I put back the grain pellet mix for him and watched to see what he would do. He would tip his bowl and try to sniff out the particular food he wants and I noticed that all this time, he would only eat the proper pellet from the grainy mix. Smart guy! Never did he eat the grains or corns or seeds or cereals that came with it. Only the actual pellet. So I went back to the pet store and asked what the brand of the pellet was that was in the grain mix and he showed me. I then started to buy that pellet with of course reading it's nutritional information first.
So my point is, maybe your rabbit doesn't like the oxbow pellet because they're used to the pellet that is in the grain mix. Unless your rabbit completely eats everything else from the grain mix, then I'm not too sure. But I know once rabbits realise that they aren't getting what they've been eating all this time, it'll leave them with no choice but to eat their "new food".
Hope this helps!
