If he is eating... then it may simply be that he is underfed.

Either way you want to ensure, as noted, that he is set up well... for a snake that small I would give closer to 5 days (rather than 5) for an acclimation, as you do want to get him feeding.

Do you know what the previous keeper was feeding and how often? As well as the date of the last feed. If not... get on the blower and find out.

Hopefully with a few good meals, and perhaps a bit of an increased feeding schedule, he may surprise you and just take off.

Bruce