I have this happen once every year or 2------- I have had lizards returned that were refusing to touch a bite and, in every case, they were eating within 10 seconds of being put back in the pen. I realize my big pen creates lizards that are basically "in the wild" but used to humans (me). It is nice to see I am not alone!!! ( not really nice- just an expression). I guess these guys get used to a setting- and resent shipping or new housing in many cases. I also think theydo beter when kept in pairs or trios ( given they have spacious housing). A lone chuck just don't act very happy & content.
I have to also think thatcovering the sides of new housing and avoid as much handling as possible is important until they get settled in.
Good Luck
David