# hline not shown in pdf

I'm using the following code but for some of the rows hlines are not shown. Appreciate if anyone can help.

\documentclass{article}
\usepackage[usenames,dvipsnames,table]{xcolor}
\usepackage{tcolorbox}
\usepackage{tabularx}
\usepackage{array}
\usepackage{colortbl}
\tcbuselibrary{skins}
\rowcolors{2}{gray!10}{white}

\tcbset{tab3/.style=
{enhanced,colframe=Gray!50!black,colback=white,colupper=black!50!black,
fonttitle=\bfseries,nobeforeafter,center title}}

\begin{document}
\tcbox[tab3,left=0mm,right=0mm,top=0mm,bottom=0mm,boxsep=0mm,
toptitle=0.5mm,bottomtitle=0.5mm,title=Test]{%
\arrayrulecolor{black!50!black}\renewcommand{\arraystretch}{1.2}%
\begin{tabular}{l|l|l}
One & Two & Three \\\hline\hline
Men & Mice & Lions \\\hline
True & False & True \\\hline
Men1 & Mice2 & Lions2 \\\hline
Men1 & Mice2 & Lions23 \\\hline
Upper & Middle & Lower
\end{tabular}}
\end{document}


• try to delete aux file and recompile. Also, if you have an old version of latex, update (I use 2016 and it is ok) – koleygr Sep 4 '17 at 21:53
• This is a known viewer issue, at certain zoom levels the lines disappear and at some other levels they appear, try with another PDF viewer and check if you encounter the same issues. – AboAmmar Sep 4 '17 at 22:12
• What is this strange rule colour – black attenuated by 50% black? A tribute to painter Pierre Soulages? ;o) – Bernard Sep 4 '17 at 22:56
• Off-topic: Since you're loading the xcolor package with the option table, there's no need to load the colortbl package separately. – Mico Sep 5 '17 at 6:05