Whites tree frog baby is not eating: took him to a vet who said that he looks just fine

[Pond Lilly]

Thank you very much for all replies! I will try a candy bowl, but I really doubt it will help. He had crickets crawling all over him and he did not care. I offered him crickets, wax worms, butterworms, moth, he just squirms and refuses to take any. He also moves his little arms, like "I do not want it! Take it away!" I can clearly see he is hungry as he sometimes has this "alert frog"look, but something seems to preventing him from actually getting it.
Here are the pictures of his enclosure, he lives in a bin, but it has a screen lid, so the ventilation should be good, I also change water once a day and clean it all once a week. In the picture he is taking his pedialite bath.
This is very stressful and I am very upset I could not figure out what is wrong. I will get the humidity up as has been suggested. Thank you!

The last time he pooped was a few days after he stopped eating, since then no poop, but the vet said she does not think he has anything in there, he is empty all the way.....

[Leefrogs]

He's probably really stressed in that bin. Height is an issue, privacy another. Mine like heavy plant cover, places to hide, and like to climb up to the top corner to sleep. I would look into getting a 20 gallon and doing a conversion(door kit) to make him more comfortable. I did a home conversion for 12$, photos are in my alblum.