Hmmmmm how long since you have had Felix before you tried his first feeding? Also when did Felix last eat for the pet store? Did you actually see Felix eat at the pet store or are you going on their word? (You wouldn't be the first to be told a young snake was eating fine when it really wasn't....in the real world we call this lying one's @@@ off...in the pet store world it's often not seen quite that way...not saying that's what happened but it's not unheard of).
I am too new to this to offer any real advice so go with the experienced people here on practical ideas as far as getting Felix on track feeding wise. Does he seem to be drinking and passing any urates or feces at all? Is he alert and using his hides to thermoregulate as far as you know?
We've never had experience with refusal to eat with our ball so our sympathies to you as I know it's a worry but they do seem to eventually eat and I'm sure someone in this forum can advise you when to worry and what signs to watch out for if you are concerned the not eating is starting to affect Felix adversely or if it lasts overly long.
~~Jo~~