Concur with the others. In the wild they might not be successful at hunting every day. Feed it to satiation once or twice a week, if it will eat, but don't sweat it.
What are you offering it?
They are also largely nocturnal so if you're trying to feed it during the day, that might not be the best time. They are much more active at night so try feeding it after lights out.
Be sure you have a cover on your tank too - they like to go carpet surfing. They can live surprisingly long out of water but it's never a good thing to have happen. If it doesn't have a hidey hole, a length of PVC works well as a cave (you can conceal it under rocks if you wish.)
Jenn