Why i cant use gallery ?

im just wondering why i cant use image gallery when im haveing 35 posts? as i remember if i have 20+ posts i can make it !!

Oh Lord, please provide them with brains!
I have no idea how often people want to ask this question within 3 months.

But ok ... here we go again.

Its between 20-50 posts.
There is no specific warranty for 20,25,30 ...