Why Can't I Do a rolling ollie?

Alright, i have been skating for a like 6 months, (I quit over the winter and spring, just got bored of it XD) and I just can't seem to do a rolling ollie. I'm not scared, I just can't do it. Anyway, I'm a goofy. When I pop the tail, I'm positive i'm sucking my knees in and sliding my foot vertically. but when I land, I land on my front foot and my back foot just sits there. I'm basically doing a split when I do this. Please help!