Dont be worried about it. Three weeks is nothing. When it becomes three months then you can be concerned although that still wouldn kill your snake. Alot of your dilema could be what youre offering and/or how youre offering it.
A useful tip: I would personaly try to avoid touching the snake before offering it food. Ya people like to suggest feeding snakes in a separate enclosure but i think its hosh posh. Honestly, ball pythons are not typicaly aggressive and its not like their ever any real threat so if you can manage to leave him put then do so. All that stuff about feeding outside of the cage so the animal doesnt mistake you for food is for the birds. That all might have sommme truth to it but its not detrimental realy. Youll have better success leaving him put. (for B.Pythons anyway) Differnt snakes react differently when it comes to feeding time. Thats why boas rock because its almost impossible to waste food when feeding boas (BCI/BCC)
Give youre snake some time to chill and keep offering food but do it quietly and carefully so as not to spook it. Snakes...especialy B.Ps in new environments get spooked easily and itll kill the mood fast.
Dont let three weeks freak you out. Try differnt methods: live, fz/th, stunned (if the mouse goes straight up to the head and annoys the snake),---keep the dead stuff about 2-3inches away from the face and be patient. Let him smell it and come after it. Tease him a little by slowly pulling away as he comes nearer. This makes them want it more.
I should be writing books on intimacy..........!!!
Hope this helps.
Brendan
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Without INTEGRITY and HONESTY what else have you!
Brendan Saffron