\documentclass{article}

\usepackage[xindy, toc, acronym, section, nopostdot]{glossaries}
\makeglossaries
\newacronym[description={Decision Support System}]{dss}{DSS}{decision support system}

\begin{document}

\newacronym[description={Decision Support System}]{dss2}{DSS}{decision support system}

Works: \glspl{dss}

Missing space: \glspl{dss2}

\end{document}
