Multiple bibliography files for each chapter with one bibliography at the end

Question

I am writing my thesis manuscript using the classicthesis package. I have four bibliography files (.bib files), one for each chapter, in a folder called "bibliographies." When I run the main file, it compiles correctly but the citations and bibliography do not appear and I do not get any error messages. So, I am not sure what the problem is. I get bold citation keys instead of in-text citations and no bibliography. I use PdfLaTeX + Bib(la)tex + PdfLaTeX (x2) + View Pdf for compilation using TexMaker.

I do not need separate bibliographies for each chapter but a single bibliography for the whole thesis.

I would be thankful to you for your assistance. Below is the information regarding the code.

I have the following code in the main file:

\addbibresource{bibliographies/chap1.bib}
\addbibresource{bibliographies/chap2.bib}
\addbibresource{bibliographies/chap3.bib}
\addbibresource{bibliographies/chap4.bib}
.
.
.
.
.
.
.
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\cleardoublepage\include{FrontBackmatter/Bibliography}

and in the bibliography.tex, I have the following code:

\defbibheading{bibintoc}[\bibname]{%
  \phantomsection
  \manualmark
  \markboth{\spacedlowsmallcaps{#1}}{\spacedlowsmallcaps{#1}}%
  \addtocontents{toc}{\protect\vspace{\beforebibskip}}%
  \addcontentsline{toc}{chapter}{\tocEntry{#1}}%
  \chapter*{#1}%
}
\printbibliography[heading=bibintoc]

and in the classicthesis-config.tex, I have the following code:

\PassOptionsToPackage{
        natbib=true,
        style=authoryear-comp,
        dashed=false,
        hyperref=true,
        backend=biber,
        %bibencoding=ascii,
        maxbibnames=10,
        giveninits=true,
        uniquename=false,%init,
        maxcitenames=2,
        parentracker=true,
        url=true,
        doi=true,
        isbn=true,
        eprint=false,
        backref=true,
        sorting=nyt,
        sortcites=true,
    }   {biblatex}
    \usepackage{biblatex}
  \DeclareNameAlias{sortname}{family-given}
% report either doi (preffered) or url (if no doi)
\renewbibmacro*{doi+eprint+url}{% 
\iftoggle{bbx:url} 
{\iffieldundef{doi}{\usebibmacro{url+urldate}}{}} 
{}% 
\newunit\newblock 
\iftoggle{bbx:eprint} 
{\usebibmacro{eprint}} 
{}% 
\newunit\newblock 
\iftoggle{bbx:doi}
{\printfield{doi}}
{}}


% remove "in:" from articles. Thanks to Herbert.
    \renewbibmacro{in:}{%
        \ifentrytype{article}{}{%
            \printtext{\bibstring{in}\intitlepunct}}}
% omit "month" and "language" from Bibliography
\AtEveryBibitem{%
    \clearfield{month}{}%
    \clearlist{language}{}%
}

% omit from all types from Bibliography

% \AtEveryBibitem{\clearfield{doi}\clearfield{issn}\clearfield{isbn}}
    %\AtEveryCitekey{\clearfield{doi}\clearfield{issn}\clearfield{isbn}}
% omit from type "articles" from Bibliography
\AtEveryBibitem{\ifentrytype{article}{\clearfield{issn}\clearfield{isbn}}{}}

    % omit from type "articles" from Bibliography

%    \AtEveryCitekey{\ifentrytype{article}{\clearfield{issn}}{}}
% some natbib backwards compatibility 
\let\citealp\cite
\let\cite\textcite

% increase vertical space between bibliography items.
\setlength\bibitemsep{0.5ex}
\setlength\bibnamesep{1.2ex}

% Comma before and after journal volume. Thanks to lockstep.
\renewbibmacro*{volume+number+eid}{%
    \setunit*{\addcomma\space}% NEW
    \printfield{volume}%
    \printfield{number}%
    \printfield{eid}}
\DeclareFieldFormat[article]{number}{(#1)}% number of a journal

% Citation Hyperlinks (not just years), thanks to Audrey.
\makeatletter
\renewbibmacro*{cite}{% Based on cite bib macro from authoryear-comp.cbx
    \iffieldundef{shorthand}
    {\ifthenelse{\ifnameundef{labelname}\OR\iffieldundef{labelyear}}
        {\printtext[bibhyperref]{% Include labelname in hyperlink
                \DeclareFieldAlias{bibhyperref}{default}% Prevent nested hyperlinks
                \usebibmacro{cite:label}%
                \setunit{\addspace}%
                \usebibmacro{cite:labeldate+extradate}}%
            \usebibmacro{cite:reinit}}
        {\iffieldequals{namehash}{\cbx@lasthash}
            {\ifthenelse{\iffieldequals{labelyear}{\cbx@lastyear}\AND
                    \(\value{multicitecount}=0\OR\iffieldundef{postnote}\)}
                {\setunit{\addcomma}%
                    \usebibmacro{cite:extradate}}
                {\setunit{\compcitedelim}%
                    \usebibmacro{cite:labeldate+extradate}%
                    \savefield{labelyear}{\cbx@lastyear}}}
            {\printtext[bibhyperref]{% Include labelname in hyperlink
                    \DeclareFieldAlias{bibhyperref}{default}% Prevent nested hyperlinks
                    \printnames{labelname}%
                    \setunit{\nameyeardelim}%
                    \usebibmacro{cite:labeldate+extradate}}%
                \savefield{namehash}{\cbx@lasthash}%
                \savefield{labelyear}{\cbx@lastyear}}}}
    {\usebibmacro{cite:shorthand}%
        \usebibmacro{cite:reinit}}%
    \setunit{\multicitedelim}}

\renewbibmacro*{textcite}{% Based on textcite bib macro from authoryear-comp.cbx
    \iffieldequals{namehash}{\cbx@lasthash}
    {\iffieldundef{shorthand}
        {\ifthenelse{\iffieldequals{labelyear}{\cbx@lastyear}\AND
                \(\value{multicitecount}=0\OR\iffieldundef{postnote}\)}
            {\setunit{\addcomma}%
                \usebibmacro{cite:extradate}}
            {\setunit{\compcitedelim}%
                \usebibmacro{cite:labeldate+extradate}%
                \savefield{labelyear}{\cbx@lastyear}}}
        {\setunit{\compcitedelim}%
            \usebibmacro{cite:shorthand}%
            \global\undef\cbx@lastyear}}
    {\ifnameundef{labelname}
        {\printtext[bibhyperref]{% Include labelname in hyperlink
                \DeclareFieldAlias{bibhyperref}{default}% Prevent nested hyperlinks
                \iffieldundef{shorthand}
                {\usebibmacro{cite:label}%
                    \setunit{%
                        \global\booltrue{cbx:parens}%
                        \addspace\bibopenparen}%
                    \ifnumequal{\value{citecount}}{1}
                    {\usebibmacro{prenote}}
                    {}%
                    \usebibmacro{cite:labeldate+extradate}}
                {\usebibmacro{cite:shorthand}}%
                \ifthenelse{\iffieldundef{postnote}\AND
                    \(\value{multicitetotal}=0\AND\value{citetotal}=1\)}
                {\bibcloseparen% Include closing parenthesis in hyperlink
                    \global\boolfalse{cbx:parens}}
                {}}}
        {\printtext[bibhyperref]{% Include labelname in hyperlink
                \DeclareFieldAlias{bibhyperref}{default}% Prevent nested hyperlinks
                \printnames{labelname}%
                \setunit{%
                    \global\booltrue{cbx:parens}%
                    \addspace\bibopenparen}%
                \ifnumequal{\value{citecount}}{1}
                {\usebibmacro{prenote}}
                {}%
                \iffieldundef{shorthand}
                {\iffieldundef{labelyear}
                    {\usebibmacro{cite:label}}
                    {\usebibmacro{cite:labeldate+extradate}}%
                    \savefield{labelyear}{\cbx@lastyear}}
                {\usebibmacro{cite:shorthand}%
                    \global\undef\cbx@lastyear}%
                \ifthenelse{\iffieldundef{postnote}\AND
                    \(\value{multicitetotal}=0\AND\value{citetotal}=1\)}
                {\bibcloseparen% Include closing parenthesis in hyperlink
                    \global\boolfalse{cbx:parens}}
                {}}%
            \savefield{namehash}{\cbx@lasthash}}}%
    \setunit{%
        \ifbool{cbx:parens}
        {\bibcloseparen\global\boolfalse{cbx:parens}}
        {}%
        \multicitedelim}}

\makeatother

% Backrefs "cited" instead of "cit"
\DefineBibliographyStrings{english}{%
    backrefpage={cited on p\adddot},
    backrefpages={cited on pp\adddot}
}