With ball pythons, just leaving it in the cage is not going to entice the snakes to eat a f/t feeder. Try using tongs and dangle the feeder in front of your snake. Wiggle it a bit. Also, just thawing it out might not be enough. I know that my snakes would rather bite at my hand than the feeder because my hand is warmer. Use a blow dryer or heat lamp to warm the feeders up before offering them to the snakes.