How old is your bun? Was he more (or less) active when he first came to you?
I found a rabbit in the woods once, my first bun as a grown up. (It’s the bun in my avatar, Bam. I also took my BB name from him. He changed my life for the better).
We could never figure out his age since he was fully adult when we found him, but it seemed pretty clear that he had been confined to a cage (or a very small area) for most of his life, and didnt really understand the concept of free roaming.
This changed, though, but he needed more than a year. He eventually became both outgoing and very cuddly. He never took an interest in toys, except in the treat ball. Treat balls are gratifying even if you fill them with the bun’s maintenance pellets, but you of course need to subtract the treat ball pellets from his daily pellet allowance.
Adult rabbits may very well lounge all day. Rabbits have a third eyelid that allows them to sleep with their eyes seemingly open (probably a good defense against predators). This means the rabbit can look wide awake even though its sound asleep .
Rabbits are crepuscular, meaning that their most active time is at dawn and dusk. Rabbits often adapt to the hoomin’s active hours though, by being mostly active in the evening (since that’s as a rule when the owners return from school or work).
Does your rabbit eat, poop and pee normally? Do you see a marked change in behavior?