Why is my Blue-tongue skink still hiding Its been 4 days

The weather might be nice, but make sure the temperature does not fluctuate too much in your skinks cage, that can make them sick.

Have you changed your flourescent bulbs recently? You won't be able to see when they go bad, but the expire after about 6 months of use. If that is the case then your skink is not getting the proper kind of light, and might be having calcium deficiencies.. hence the poor shedding. If the weather is nice enough, take it outside for a couple hours during the brightest part of the day. Keep it in a cardboard box or something like that, as glass aquariums over heat very quickly in the sunlight. Also, change out your bulbs with high quality reptiles flourescent tubes.

Also, make sure you're giving it a varied diet, not just bottled skink food or the same crickets every day. If you get crickets from a store, make sure to feed the crickets high quality cricket food before you feed them to the skink. Many pet stores do not feed their crickets after they get in. Since the crickets have empty stomachs, the skink that eats them is getting "empty calories" from the crickets, with no nutrition. Also try coating the crickets with some vitamin suppliments. If you get the crickets from outside, make sure no one is using pesticides in your area.