Quote Originally Posted by DrDooLittle View Post
I would try a small rat pup/pinkie in the enclosure overnight. Small pup/pinkie, will have its eyes closed
Actually what you refer as pup will not have their eyes closed pups are the size of an adult mouse are 2 weeks old and gave their eyes open way too large additionally, when a very young hatchling does not eat he will respond better to mice.

To the op do not offer a larger enclosure, 6 quarts should be your maximum, switch to aspen bedding if you haven't already, and one hide such as small plastic flower pot saucer will be enough, and try the brown paper bag method.