Question About Ranking For My Authority Site

I have an authority site that I launched about 4 months ago. <--- (just to elaborate, I am well aware my site is not considered an "authority" by Google for a competitive keyword phrase while only 4 months old. I am simply referring to it as an authority site because that is what I had in mind while launching it, I plan to shoot for making it an authority in the specific niche the site is centered around over the course of a long period of time. I understand back links as well as other off-page SEO elements are needed to achieve this, and it will not be an easy task; I am not concerned about that.)

It is a blog platform that deals in a fairly competitive niche.
I have the homepage optimized for a specific phrase with about 120 supplemental posts that I have been gradually adding on a weekly basis.

My problem is; my website shows up for quite a few long tail keywords, so I know I have not been de-indexed or anything.
However, for my main phrase; whenever I run a rank checker there is no trace of my website anywhere for that keyword. <--- (I understand that my site is not going to be anywhere close to the top 100 pages of Google, I am just confused as to why it is not showing up ANYWHERE)

I have not done a whole lot of back linking for this site, just have been letting it age and gain some natural authority through article syndication. I just want to ensure that this is simply a matter of the site ranking so far into oblivion currently that the rank checkers simply do not pick it up? Or is there some underlying problem I am not aware of?

Is this fairly common for low authority sites working their way into a competitive niche? Just want to make sure that when I do eventually start my back linking campaigns for my site that it will eventually start showing up.