After researching this problem I could not find any solutions so I have had to resort to asking it myself.
The problem is that citations are not working at all when using natbib. I have done the following:
Bibliography.bib file with a sample bib code:
@article{Reference1,
Abstract = {We have developed an enhanced Littrow configuration extended cavity diode laser (ECDL) that can be tuned without changing the direction of the output beam. The output of a conventional Littrow ECDL is reflected from a plane mirror fixed parallel to the tuning diffraction grating. Using a free-space Michelson wavemeter to measure the laser wavelength, we can tune the laser over a range greater than 10 nm without any alteration of alignment.},
Author = {C. J. Hawthorn and K. P. Weber and R. E. Scholten},
Journal = {Review of Scientific Instruments},
Month = {December},
Number = {12},
Numpages = {3},
Pages = {4477--4479},
Title = {Littrow Configuration Tunable External Cavity Diode Laser with Fixed Direction Output Beam},
Volume = {72},
Url = {http://link.aip.org/link/?RSI/72/4477/1},
Year = {2001}}
I then created a test tex file:
\documentclass[]{article}
\usepackage[square, numbers, comma, sort&compress]{natbib}
\begin{document}
\title{Title}
\author{Author}
\date{Today}
\maketitle
Content
test. \citet{Reference1} \cite{Reference1} \citet*{1.01} \citet{Reference2} \citet{Reference3}
\label{Bibliography}
\bibliographystyle{unsrtnat} % Use the "unsrtnat" BibTeX style for formatting the Bibliography
%\bibliographystyle{plain}
\bibliography{Bibliography} % The references (bibliography) information are stored in the file named "Bibliography.bib"
\end{document}
Yet still the output is as follows:

As per the above figure, you may notice that even the enumeration in the bibliography is not working correctly.
What could be the problem please ?
Test Project Contents: Bibliography.bib, test.tex. Moreover, I am using Latexian
LOG:
This is pdfTeX, Version 3.14159265-2.6-1.40.15 (TeX Live 2014) (preloaded format=pdflatex)
\write18 enabled.
entering extended mode
(/Users/Wiltabone/Desktop/Test/TSWLatexianTemp_000017.tex
LaTeX2e <2014/05/01>
Babel <3.9k> and hyphenation patterns for 78 languages loaded.
(/usr/local/texlive/2014/texmf-dist/tex/latex/base/article.cls
Document Class: article 2007/10/19 v1.4h Standard LaTeX document class
(/usr/local/texlive/2014/texmf-dist/tex/latex/base/size10.clo)) (/usr/local/texlive/2014/texmf-dist/tex/latex/natbib/natbib.sty) (./TSWLatexianTemp_000017.aux)
Package natbib Warning: Citation `Reference1' on page 1 undefined on input line 13.
Package natbib Warning: Citation `Reference1' on page 1 undefined on input line 13.
Package natbib Warning: Citation `1.01' on page 1 undefined on input line 13.
Package natbib Warning: Citation `Reference2' on page 1 undefined on input line 13.
Package natbib Warning: Citation `Reference3' on page 1 undefined on input line 13.
(./TSWLatexianTemp_000017.bbl
Underfull \hbox (badness 1102) in paragraph at lines 23--28
[]\OT1/cmr/m/n/10 Carl E. Wie-man and Leo Holl-berg. Us-ing diode lasers for atomic
)
Package natbib Warning: There were undefined citations.
[1{/usr/local/texlive/2014/texmf-var/fonts/map/pdftex/updmap/pdftex.map}] (./TSWLatexianTemp_000017.aux
Package natbib Warning: Citation(s) may have changed.
(natbib) Rerun to get citations correct.
Thanks