A) hoppers are WAY too small
B) you don't force/assist feed adult snakes, they already know how to eat. Honestly that was probably a setback and will make things harder moving forward.
C) adults often take a while to get back to eating after changing homes.
D) you want to be consistent in your offerings. Your best bet is to find out what the snake was eating prior to coming to you. Feed exactly the same. You may even want to mimic the previous setup as identical as you can.
The weight loss isn't extreme. Just be patient. A snake that knows how to eat will not starve itself to death.