Citation with Biber and BibLaTeX

Question

I am now struggling for 2 days with the bibliography and citation in biblatex. After compiling there is no bibliography and instead of citation the cite-key appears in bold. The following shows parts of the codes used:

\documentclass[11pt,ngerman,titlepage]{article}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage[ngerman]{babel}
\usepackage[extendedfeature=title]{scrextend}
\usepackage[left=2cm, right=2.5cm, bottom=3cm, top=3cm]{geometry}
\usepackage{graphicx}
\usepackage{caption}
\usepackage{textcomp}
\usepackage{gensymb}
\usepackage{subcaption}
\usepackage{wrapfig}
\usepackage{layout}
\usepackage[onehalfspacing]{setspace}
\usepackage{cleveref}
\usepackage{placeins}
\usepackage{comment}
\usepackage{lscape}
\usepackage[nohyperlinks, printonlyused, withpage]{acronym}
\usepackage[babel, german=quotes]{csquotes}
\newcommand*{\mcite}[1]{\citeauthor{#1} (\citeyear{#1})}
\usepackage[backend=biber,citestyle=apa]{biblatex}
\addbibresource{srmbiber.bib}
\begin{document}
My cite atempt \cite{Keith2015}
\printbibliography
\end{document}

My .bib file: srmbiber.bib looks like this:

@Article{Keith2015,
    author  = {Keith, D.W. and MacMartin, D.G.},
    journal = {Nature Climate Change},
    title   = {A temporary, moderate and responsive scenario for solar geoengineering},
    year    = {2015},
    number  = {3},
    pages   = {1758-6798},
    volume  = {5},
    doi     = {10.1038/nclimate2493},
    url     = {https://doi.org/10.1038/nclimate2493},
}

I allready tried the following:

• compile with pdflatex - biber - pdflatex - pdflatex
• change the settings in my editor (texstudio), so that biber is the default
• backend=bibtex
• looked into various log files (.blg is empty)

Repeating error messages:

• .bbl not created (though I found it and it was empty)
• Invalid or undefined BibTeX entry key in file...

Does anyone have an idea, what the problem might be about?