please, consider the following two mwe-s:
the first:
\documentclass{article}
\usepackage{siunitx}
\usepackage{cellspace}
\setlength\cellspacetoplimit{5pt}
\setlength\cellspacebottomlimit{5pt}
\addparagraphcolumntypes{X}
\usepackage{tabularx}
\begin{document}
\begin{tabularx}{3cm}{X Cc c}
\hline
A & 123 & 456 \\
\hline
\end{tabularx}
\end{document}
the second:
\documentclass{article}
\usepackage{siunitx}
\usepackage{cellspace}
\setlength\cellspacetoplimit{5pt}
\setlength\cellspacebottomlimit{5pt}
\addparagraphcolumntypes{X}
\usepackage{tabularx}
\begin{document}
\begin{tabularx}{3cm}{CX c c}
\hline
A & 123 & 456 \\
\hline
\end{tabularx}
\end{document}
the first one work as expected, the second one throw error:
! Package array error: Illegal pream-token (\ecolumn): `c' used.
apparently specifier CX
doesn't work as i expected. what i doing wrong?
C{X}
instead ofX
in the\begin{tabularx}{3cm}{...}
spec.p{3cm}
are given whereS{...}
is mentioned), that's why I just said “it works for me” and didn't propose it as an answer...