Most often, I read that they will not react to it unitl they are about a year old. My older cat could care less about catnip until she was at least 2 years old. My four month old kitten has already shown an interest...(she smells it and licks it and rubs all over on the floor when it's around).
I think it depends on the cat, but your kitten's reaction is NOT uncommon. Some cats never grow to like it, but usually it just takes time.