Why doesn't my baby Savannah monitor EAT.?

Well we got him on monday and a baby jackson chameleon from a breeder on recycler, we emailed him because it's been 3 days and he did not want to eat and he said he eats crickets, we tried to feed him crickets and he didn't want any at the time but now it's been 3 days and I am worried this is a sick monitor or maybe he is stressed out. The chameleon ate well and they have a 4 ft long Savannah monitor outside, so they know what they are doing. Maybe I am at fault which is why I came here to ask, WHY ISN'T HE EATING anything? He is a juvenile or baby monitor maybe he just drinks and eats weekly. IDK, what's going on with it. He didn't like his tank, and then I made him a bigger tank and now he seems more chilled out, but he is still not eating crickets. People Help me.