There are many many reasons a ball can go off feed. The most important thing that YOU can do in this situation is be sure that your bp is set-up correctly and has the proper husbandry. No handling is also a good idea until your bp is feeding again.

You should have a cool side in the low 80's a warm side between 90-93 F and identical hides at each end. You should have 50-60% humidity and both humidity and temperature are best read with digital gauges. A UTH requires a control such a thermostat or rheostat. A low traffic area is ideal for your enclosure, and to increase security for your snake, cover three sides of the tank with paper/cardboard/anything you would like to use.

To increase your bps sense of security during feeding, turn off the lights so it is nice and dark, if you feed f/t be sure it is nice and warm (not hot - you don't want to cook it). Leave the snake alone once the prey is in the enclosure, and with live prey simply keep an eye from a distance/and or sit quietly.

There are more tips that can be given, I hope I have helped you get started.