ModaLisp doesn't show graphs



I’m having a problem with Modalys (ModaLisp) and it’s graph windows not opening when running a script. I’m new to Lisp so this might be a user error but Modalys won’t open any graphs even when running an example script such as “ex2 - plate and hammer (plot)”. I have two computers, one with High Sierra and another with Mojave and the same thing happens with both of them.