There is no minimum post requirement, it is only four days. If I had to guess why you dont have access it would be that you registered when there was a post count limit but never met the requirement before things changed. Since you were registered for more than four days the system did not pay attention to you but you still could not post since you never had the ability before.
In short, an admin (
Gaz or
Artashes) can manually give you the access you need.