A 55 gallon is too big. Move him down to a 10 gallon with hide. Whenever receiving a new snake it is wise to leave it alone for 1-2 weeks before feeding. That means no handeling also. Assist feed should always be done before force. All depends on his overall look. If he is healthy looking and doesnt look skinny then could probably wait a little while before offering food. I would go a week inbetween feeding also. A lot of ball pythons are more enticed to take a live rodent over a dead one so i suggest finding a live rat and offering that first. If he still aint eating and looks skinny and unhealthy then assist feed him. Take a F/T pinky rat and rub the nose of it on the snakes mouth to open it. Take a pair of tongs and grab the rat by the head and slowly and carefully move the rat into the snakes throat. Then place snake back into enclosure. The trick here is that the rat gets stuck down in his throat to a point the ball python finally realizes he cant spit it up then starts taking it down on his own. Good luck!