How is his behavior? Does he seem nervous or scared? He has transitioned to a new environment, so it may take some time for him to feel safe enough to eat. Notably, I would recommend against pellets that have veggies and fruit mixed in — rabbits are selective foragers, so a rabbit will learn to only eat the “treat” bits in it and not the actual pellets, which have the nutrients they need.
How are you offering hay? You want to offer a lot of hay, and putting it in more places can help activate a rabbit to go around and forage for the best pieces. Hay isn’t like a “normal” food either, in that you inevitably need to throw some away regularly because a rabbit, based on its senses, will simply not eat some pieces, so don’t expect to only refill when there is no hay left. Recycling, mixing, and re-distributing hay is a good tactic (but remember to throw away any soiled (peed on) hay!).
Also, a rabbit will typically always eat pellets and veggies first before hay, and pellets are filling and more “treat” like, in comparison to hay. To encourage more hay, you want to limit how often the rabbit has access to non-hay foods, as many default to just eating pellets, which isn’t good. I recommend offering pellets in the morning and and night, but then for the remainder of the day, the rabbit only has access to hay.
If he is having an appetite to eat a small apple treat when offered, it’s a good sign that he has an appetite and energy. If he ever refuses a treat and doesn’t eat anything for 12 hours, that is an emergency and he needs to be taken to the vet.
Could you describe your set-up and routine for him? That can help.
The answers provided in this discussion are for general guideline purposes only. The information is not intended to diagnose or treat your pet. Seek the advice of your veterinarian or a qualified behaviorist.