Biber doesn't run on \inputted files - any thoughts?

[GreenVeggi]

I cannot get Biber to run on a file where I \input multiple .tex files in the root file. If I were to run a MWE like so

    % !TeX TXS-program:bibliography = txs:///biber
    \documentclass[a4paper,style=index]{book}
    \usepackage[T1,LGR,T2A]{fontenc}
    \usepackage[utf8]{inputenc}
    \usepackage[greek,russian,main=british]{babel} % Compile w/PDFLaTeX !!!!!
    \languageattribute{greek}{ancient}
    \usepackage{cjhebrew}
    
    \usepackage[top=3cm,bottom=3cm,left=3cm,right=3cm,columnsep=30pt]{geometry} % Document margins and spacings
    \usepackage{amssymb}
    \usepackage{enumitem}
    
    \usepackage{amsmath}
    \usepackage{tikz}
    \usepackage{epigraph}
    \usepackage{csquotes}
    
    \usepackage[style=apa, backend=biber, useprefix=false]{biblatex}
    \AtEveryCitekey{\toggletrue{blx@useprefix}}
    \setlength\bibitemsep{\baselineskip}
    \bibliography{references.bib}
    \addbibresource{references.bib}
    
    \usepackage{fancyhdr} % Required for modifying headers and footers
    \fancyhead[L]{\rightmark} % Top left header
    \fancyhead[R]{\leftmark} % Top right header
    \renewcommand{\headrulewidth}{0pt} % Rule under the header
    \fancyfoot[C]{\textbf{\thepage}} % Bottom center footer
    \renewcommand{\footrulewidth}{0pt} % Rule under the footer
     % Use the custom headers and footers throughout the document
    
    \usepackage{xcolor}
    \usepackage[linktoc=all, colorlinks]{hyperref}
    
    \usepackage[acronyms,nopostdot]{glossaries} % allows glossaries
    \input{glossaries}
    \makeglossaries
    
    \begin{document}
        This is a sentence with an \acrfull{acronym} \parencite{bellbottom}.
    \end{document}

having defined \newacronym{acronym}{acr}{acronym} (separate .tex) and @book{bellbottom,author= ...} (in a .bib file), everything goes well.

If the last part looks like you'd expect in a bigger document, however, like so

    \begin{document}
        \input{intro.tex}
        \printbibliography
        \printglossary
    \end{document}

the rendered PDF shows a bold citekey in parentheses. This excellent guide tells me to look for a .blg file, which I do not get with the \input example.

I compile: pdfLaTex → makeglossaries → biber → pdfLaTex → pdfLaTeX. I'm working with VS Code (1.71.2) and MikTeX (22.8.28).

    {
                "name": "biber",
                "command": "biber",
                "args": [
                    "%DOCFILE%"
                ],
                "env": {}
            }

Have any of you had similar issues?