I cannot use \tex inside the \title{...} since it fails on the \maketitle command. When I remove the \tex, the file is built correctly.
\begin{titlepage}
\title{
\normalfont
\LARGE University name \\[25pt]
\rule{\linewidth}{1pt} \\[0.4cm]
\huge Semestral work XXX \\
\rule{\linewidth}{1pt} \\[0.6cm]
\Large Rewritten in the \tex typesetting system \\[0.5cm] % probable cause %
}
\author{Nikolas Charalambidis}
\date{\normalsize{7. 5. 2019}}
\maketitle % failing %
\thispagestyle{empty}
\end{titlepage}
The error is (I use TexMaker):
Undefined control sequence.@title ...\[0.6cm] \Large Rewritten in the \textypesetting system \[0.5cm] \maketitle
\title{stuff}and\maketitleto get the predefined title page; or usetitlepageto define a title page of your own. Do not mix them up. – Johannes_B May 09 '19 at 06:52