When my ig gets stressed from moving or any outside influence he'll do the same. However, I've found that they absolutely cannot resist grapes and bananas. The darker the banana the better. If I run a cut grape on his snout he will instantly lick it and search for more. To solve his stress I do the same you've done, quiet area, proper temps etc. When a few days pass and he's still not interested I'll get a banana and grapes and make kind of a gooey mixture with his regular greens. He will smell the fruity smells and he can't resist. Hope that helps!