I have an accepted paper in a journal. The paper contains an equation with two labels. We have typeset the paper using the journal's style files and it all looked perfect. We can reference both labels, click on any one of them, and we will be taken to the displayed equation.
But now the copyeditors are saying that if we have two equation labels on a line, then in the typeset online version we can only get a hyperlink to ONE of them. Either to the first label, or to the second label. The reason they give is that they are using A++ to typeset the paper. I am not sure what A++ is, but I do not understand why they could not give hyperlinks to both equation labels.
Here is an MWE. This works for me, but not for the journal.
\documentclass[10pt]{article}
\usepackage{empheq}
%\usepackage[latin1]{inputenc}
\usepackage[margin=3.0cm]{geometry}
\usepackage[pagebackref=false, colorlinks=true, linkcolor=blue, citecolor=blue, linkcolor=blue, anchorcolor=red, urlcolor=blue]{hyperref}
\makeatletter
\newcommand{\leqnomode}{\tagsleft@true}
\newcommand{\reqnomode}{\tagsleft@false}
\makeatother
\begin{document}
\begin{center}
\begin{minipage}{0.6\linewidth}
\leqnomode
\begin{equation}\label{primal}
\hspace{-3cm}
\begin{split}
\max & \,\, c^\top x \\ %C \bullet X \\
s.t. & \,\, A x \leq b \\
\end{split}\tag{P}
\end{equation}
\end{minipage}%
\begin{minipage}{0.5\linewidth}
\begin{equation}\label{dual}
\begin{split}
\min & \,\, b^T y \\
s.t. & \,\, A^\top y = c \\
& y \geq 0
\end{split}\tag{D}
\end{equation}
\end{minipage}
\end{center}
\newpage
Reference \eqref{primal} here. Reference \eqref{dual} here.
\end{document}