Definitely agree with this. 55 gal seems too big for a ball python, unless its a huge adult female. Keep him in the 20 gal imo. Also, you definitely want to black out three sides of any glass tank you keep a ball python in. Glass tanks look nice but dont serve their purpose too well. When all 4 sides are exposed, your BP may feel insecure and may not eat for this reason.
I have a friend whos had his ball python for around 8 months. First 5 months, his bp ate two times out of five attempts. Pretty stupid that he only tried feeding him five times in five months but ANYWAYS... after I gave him a bit of advice, he got two identical hides, blacked out the sides, started thawing properly and offering the appropriate sized meals, his ball python hasnt missed a meal since! Not saying proper husbandry fixes all feeding problems though, but it definitely is a good starting point!