The above poster gave you some great information. I had this similar problem with a .1 hatchling I recently purchased. She'd strike, coil, then release the live prey. I noticed that if there was ANY sudden movement after she coiled, it'd scare her and she immediately uncoiled. Even when I tried to put the lid back on her tub it spooked her enough to uncoil.
Like ^ said, get the husbandry spot on and try feeding him/her again in 5-7 days, don't make any sudden movements after she coils and see if it works.