I am using XeLaTex engine , it compiles but neither citations nor bibliography are showing in output document
\documentclass{article}
\usepackage[a4paper, margin=0.75in]{geometry}
\usepackage{multicol,caption}
% Figure
\usepackage{graphicx}
\usepackage{lipsum}
\graphicspath{ {./images/} }
\newenvironment{Figure}
{\par\medskip\noindent\minipage{\linewidth}}
{\endminipage\par\medskip}
\usepackage{polyglossia}
\setdefaultlanguage{english}
\setotherlanguage{arabic}
\newfontfamily\arabicfont[Script = Arabic]{Simplified Arabic} % Replace 'Simplified Arabic' with a font from your system
%--------------------------------
%in the preamble
\usepackage{biblatex}
\usepackage[autostyle]{csquotes}
%--------------------------------
\addbibresource{sample.bib}
\begin{document}
\maketitle
\begin{abstract}
This is my abstract
\end{abstract}
\begin{multicols}{2}
\section{Introduction}
Introductin ......
\begin{Arabic}
\begin{tabular}{|c|l|}
\hline
Central Kurdish (Soraní - modified Arabic) & \# \\ \hline
ئا ـا ا & 1. \\ \hline
\end{tabular}
\end{Arabic}
\end{multicols}
\begin{multicols}{2}
\section{PHASES OF DESIGNING MRWL}
Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book
\end{multicols}
\begin{multicols}{2}
Cite here \cite{einstein}. \cite{einstein}.
\printbibliography
\end{multicols}
\end{document}
=====================
This is sample.bib
@article{einstein,
author = "Albert Einstein",
title = "{Zur Elektrodynamik bewegter K{\"o}rper}. ({German})
[{On} the electrodynamics of moving bodies]",
journal = "Annalen der Physik",
volume = "322",
number = "10",
pages = "891--921",
year = "1905",
}
@book{latexcompanion,
author = "Michel Goossens and Frank Mittelbach and Alexander Samarin",
title = "The Companion",
year = "1993",
publisher = "Addison-Wesley",
address = "Reading, Massachusetts"
}
@misc{knuthwebsite,
author = "Donald Knuth",
title = "Knuth: Computers and Typesetting",
}

Simplified Arabicso I usedNotoNaskhArabic-Regular.ttf, but other than that the example compiles for me and produces a bibliography with one entry (einstein). (This is expected since LaTeX only lists references that were\cited or\nocited in the bibliography, see https://tex.stackexchange.com/q/17128/35864.) Did you run LaTeX, Biber, LaTeX, LaTeX on your document? See https://tex.stackexchange.com/q/63852/35864 and https://tex.stackexchange.com/q/154751/35864. – moewe Mar 21 '20 at 06:34\DeclareLanguageMapping{UKenglish}{british}is not required (or at least it should not be required; I would consider it a bug if you need it) and that the example.bibentries are not of the highest quality when used withbiblatex. Thedoifield should only contain the DOI and not the full URL:doi = {10.1002/andp.19053221004},would be better. There should be no need to escape special characters in theurlfield, sourl = {http://www-cs-faculty.stanford.edu/~uno/abcde.html},would be correct. – moewe Mar 21 '20 at 07:14