He’s used to using his corner, and won’t follow the litter pan in another spot. From his viewpoint, you’ve put something in the way of his toilet, so he’ll use it or move it.

All I can suggest at this age is to try 2 things: first, you can try a litter pan that has a lower opening on one side, so he doesn’t have to jump high to get into it. Make sure it’s big and roomy (not like a cramped corner one). Some are even made with the screws that attach to the cage sides. But as he gets older he may find it harder to jump in, so if he has a low front one now, he’ll be comfortable for years to come.

Second, try positive reinforcement. I’m working on this with my Sammy now. When he uses the litter pan, say Litter Pan, Good Bunny and give him a small reward, like a raisin or a pellet. Keep putting the pan back in his corner when he moves it, and when he uses it again, reward him. After a few days, don’t reward with treat every time, but still praise him. Make the treat unpredictable, so he knows that he may get one, he may not, but he will possibly get one if he just keeps using the litter pan.
Punishment and negatives don’t work with bunnies, but they’re smart, so positives usually work in training.