The following makes it work;  it uses the option -lt instead of the option -ll

#!/bin/bash

exec maple_in_filter | maple -lt  -l p=calc -c 'interface(plotoptions=\"portrait,color,width=300,height=200\")' | maple_filter


The reason why the option -ll does not work might be related to the following:

Suppose the file useme.txt contains the following

\begin{mapleinput}
2*3;
\end{mapleinput}

If you run the command

cat useme.txt | maple -lt

you get

\begin{mapleinput}
2*3;
\end{mapleinput}
\begin{maplettyout}
                                       6
 
\end{maplettyout}


But if you run the command

cat useme.txt | maple -lt

you get the message

\begin{mapleinput}
2*3;
\end{mapleinput}
\begin{maplelatex}
 
\end{maplelatex}
\begin{maplettyout}
Printing error, unable to load requested fonts
\end{maplettyout}


Therefore, what seems to be happening is that some fonts are not loaded; this could be due to how maple was installed.

Maybe maple_filter gets confused with this.