We went into our lfs
the other week and spotted a very unhappy porcupine puffer sat motionless in the corner of his tank. We told the owner about him and he just said "he's fine, just sulking. He won't eat for about a week either. Sometimes you just have to starve them out."
To be honest, I didn't believe him. It looked like one seriously I'll puffer. W went back the next week and he was swimming around, curious about everything and checking us out
so the answer just seems to be to just wait it out. He's probably just a bit stressed from the move, but when he's hungry enough he'll eat
And on the subject of porcupine puffer size. I've just read an article in practical fish keeping magazine about tankbuster marines. Porcupine puffers are included because they can get to 91cm. That's about 3 foot. If you were to stand it with it's tail to the floor, it's head would reach to your waist. That's one huge fish!