i had the same problem
read everything but nothing prevailed
untill i tried one thing
well, it worked anwyays.
i found him hiding and couldnt find him, would eat ut not much strangely enough.
during winter, i thought it was too cold so i bought two ulbs, 100w each. bought the temp from a 21 to22 o about 25 to 27 and basking spot two places was alot higher of course.
i found that he hid most of the time.
it was too hot!!!!
in the peak of winter, he didnt eat much it was too cold, so i increased it, but it was warming up and got too hot, i removed second bulb and he came out literally two days or less later.
maybe the tank is too hot, how do you keep the tank 'warmer' at night?
cos i found that, in the australian desert and stuff, where they are, it isnt 25 to 26 at night, it goes down way lower than that, so naturally i guess their body is accustomed to fluctuation in temp i guess.
well this worked fo rme. perhaps trying to lessen heat?