So I tried using a JS problem that does work on my machine, namely here.
When I load this problem in any of the browsers on my computer, it works fine. When I copy all the files and their dependencies (including all the .pl files) to my local course, the canvas element does not appear.
For an even easier example of what I'm talking about, if I copy the graph_line.pg file available in this thread and try to use it as a problem in my course, once again the graph object does not display. This example is easier because there are no other files necessary for it to work.
Any and all help is appreciated.