Two weeks isn't very long yet. If he spends his daytime outside, perhaps he doesn't feel that indoors is his territory, so doesn't feel he should explore it.
Perhaps he wears himself out and is too tired in the evening.
Two of my buns hate being indoors - I only bring them in on firework nights, and once when one wasn't well. They sit still most annoyed, and won't venture far.
Perhaps yours wants to be an outdoor bun all the time! Does he ever free-range in the garden? Is he an adventurous bun, exploring his surroundings?
Other than that, perhaps a little more waiting time, and a trail of goodies leading away from the cage door might encourage him out. I am sure he will surface when he feels safe to do so... but it might take some time. He is still learning to trust you as well as the rest of his world.
Try teaching him to take food pellets from your hand, then perhaps he will follow a hand with food in??