Rabbit won’t poop in litter box

I’ve recently gotten my bunny, and she’s been a little handful in the 5 days I’ve had her. But a handful in a good way Anyway, the only problem I really have is that she won’t poop in the litter box (I mean, she will, but DEFINITELY not as much as she poops anywhere else). She will poop RIGHT next to it, but not in it. When I first got her, it wasn’t that bad, but then I blocked off her access to under my bed, and she started pooping all over my floor and also started covering her cage in poop (she’s completely free roam, I just use a dog kennel as a little home base area). She’s really good about peeing in the litter box, though, which doesn’t quite make sense to me. She’s not old enough to get spayed, which I know really helps with litter box training, so are there any tips you can give me in the meantime? I’d greatly appreciate it!

Just make her space smaller and then slowly expand the area when she pick up the habit.

Having hay and food near the litter box will keep it in one place also. They often poop when eating.

She’s also in a new home, so she’s just marking and telling everyone she lives there. Just keep up with the cleaning and dump the droppings in the litter box.

I too would start with a small space, keeping her in the cage with the litterbox for some days, then expanding her area gradually. Free roam right away is cute, but imho it's better to learn first what her base, litter box, etc. is, then let her explore from there.
Right now everything is her place, not common ground, so why not poop wherever she likes, territory needs to be marked...

There will always be stray bunny berries, one of the joys of having free roam rabbits, but there shouldn't be piles of it getting replaced after every cleaning.

May get better with age anyway, how old is she? Spayed?

While you are litter training your bunny, he or she will have to stay in an enclosed area. So, before you start training, choose and prepare the training area. A bathroom, utility room, or other small room without carpeting is a good place to start the training. You can also use a cage or something. Maybe a cardboard box?!
Use 1" of litter covered with Timothy hay. Add in some of the rabbit's poops and urine-soaked paper or hay. Place the litter box whereever the bunny seems to prefer to use, which is often a corner.
And please expand the area. Remember rabbits graze at large in wild.