My new Green Iguana will not eat and has not defecated. What should I do?

How long have you had it? If you just got it in the last couple of days, don't worry. It takes time for them to get accustomed to their new home. Just be sure that you have set up the proper habitat and that the temp is at least 95 deg. Put a shallow plate of orted small bits of fruits and veggies and leave it for him to eat when he wants. Remove it daily even if he has not eaten any of it and replace with fresh. Make sure you have clean fresh water available. Don't bother him too much for a few days, and he should be fine.