This animal is not near sexual maturity based on it's size so refusal is not the reason, hopper are what are fed right out of the egg, this animal is not right out of the egg either.
OP
Feeding issues with new owner are generally husbandry related, at this size your animal should be voracious.
The keys are
Optimum husbandry, proper temps, measured with a digital thermometer and at the surface of the substrate.
An enclosure that is not too big, too big means the animal will stress over time and refuse to feed.
Proper hides very tight providing the required security.
Minimum stress which often means minimum handling if you are experiencing issues.
Proper food size until the animal is 500 grams is a prey equal the girth size
Changing prey (F/T to Live) or Mice to rats or vice versa) may work however this means you must be able and willing to do this in the long run, if not keep feeding what used to work.
At this size this is the setup I would suggest, or 15 quarts max https://ball-pythons.net/forums/show...-hatchling-101 and appropriate size meal https://ball-pythons.net/forums/show...ing-Guidelines