I do not think the posts in the ads section count towards the post count. If @OJ North Jersey participated in the discussion forums he would gain the ability to send PMs. I think it is 10 posts minimum.
Not sure why your profile shows zero posts, but clicking through to 'activity' shows your your posting history on this forum goes back 13 months, and consists of over two dozen posts asking sellers to message you because you are too new to post.