empty bibliography

My preamble

\documentclass[12pt,a4paper]{report}
\usepackage[utf8]{inputenc}

\usepackage[english,greek]{babel}
%\usepackage[square, numbers, comma, sort&compress]{natbib}  % Use the "Natbib" style for the references in the Bibliography
\usepackage{verbatim}  % Needed for the "comment" environment to make LaTeX comments
\usepackage{biblatex}
\usepackage{amsmath,amsfonts,amssymb,amscd,mathrsfs,enumerate}
\usepackage{amsthm}
\usepackage{tikz}
\usetikzlibrary{matrix}
\usepackage[all]{xy}
\usepackage{relsize}
\usepackage{pifont}
\usepackage{mathtools}
\usepackage[all]{xy}
\usepackage{relsize}
%\usepackage{fourier}
\usepackage{esvect}
\usepackage{csquotes}
\usepackage{substitutefont}
\usepackage{graphicx}
\substitutefont{LGR}{\rmdefault}{artemisia}
\usepackage{pgf,tikz}
\usepackage{mathrsfs}
\usepackage[capposition=top]{floatrow}
\renewcommand{\qedsymbol}{\textcolor{black}{$\blacksquare$}}
\allowdisplaybreaks
\usepackage{thmtools}

\useshorthands{;}
\defineshorthand{;}{?}

\usepackage{biblatex}


then before the \end{document} I wrote

\nocite{*}
\printbibliography


but nothing appears (the bibliography does not appear) and I get an error "empty bibliography on imput line 616".

Any help?

Maybe this helps

[0] Config.pm:304> INFO - This is Biber 2.12
[0] Config.pm:307> INFO - Logfile is 'output.blg'
[43] biber:315> INFO - === Sat Oct 19, 2019, 07:04:29
[75] Biber.pm:371> INFO - Reading 'output.bcf'
[180] Biber.pm:886> INFO - Using all citekeys in bib section 0
[204] Biber.pm:4093> INFO - Processing section 0
[217] Biber.pm:4254> INFO - Looking for bibtex format file 'bibl.bib' for section 0
[219] bibtex.pm:1523> INFO - LaTeX decoding ...
[229] bibtex.pm:1340> INFO - Found BibTeX data source 'bibl.bib'
[255] bibtex.pm:94> FATAL - Caught signal: SEGV
Likely your .bib has a very bad entry which causes libbtparse to crash: Operation not permitted

• Did you run Biber? You need to compile your document with LaTeX, Biber, LaTeX, LaTeX (where LaTeX can be your favourite flavour of LaTeX: pdfLaTeX, XeLaTeX, LuaLaTeX). See tex.stackexchange.com/q/63852/35864 for a more in depth explanation. See tex.stackexchange.com/q/154751/35864 for help in getting your editor to run Biber for you. Oct 19, 2019 at 7:23
• @moewe Thank you! I write it online in overleaf. Do you know where I can see the compiler I use? Oct 19, 2019 at 7:30
• Overleaf automatically runs Biber for you. In that case there must be an error somewhere. Download the .blg file (shown in tex.stackexchange.com/q/462314/35864 for the .bbl) and post its complete contents here. Oct 19, 2019 at 7:32
• Er, so what was the answer? Oct 19, 2019 at 8:46
• Not sure if I understand correctly, but if you found the solution, please consider writing an answer below and accepting it so that other people can benefit from it as well. Oct 19, 2019 at 10:21