Well if all else fails there is always coaxing the rabbit out with some parsley or cilantro! My rabbits will go anywhere there is parsley orcilantro.Especially Oreo!
If he is really young just a tiny bit as I think that the younger ones are supposed to be introduced to vegetables at a certain time. Also, from what I have experianced, rabbits can have extremely sensitive digestive systems. My rabbit Miley, gets an upset stomach if there is something new, if she is nervous, if something scares her. So be really careful and slow about introducing new veggies and the qty. Oh I just read he is a year old. So you don't have to be as cautious as a rabbit that is months old.
Welcome to the forum! And good luck getting your rabbit out.
Shannon