@Alejandro Jakubi I tried all of Alejandro's test and the data structure was indeed properly created and the plotsetup(char) command produced the correct output. However, the plot was still blank.
However: I have found the solution. If I include a "linestyle" plot option within the line command, it works properly. I can choose solid or dash or whatever and it works but if I leave that plot option out, as I would normally do, it fails to plot anything. In the plane, there is no such issue but in space this is what I have discovered.
In other words: line([0,0,0],[1,1,1]) produces no visible output but line([0,0,0],[1,1,1],linestyle=solid) does. In the plane line([0,0],[1,1]) works without the plot option of choosing a line style.
Is this a bug or a feature? Can it be fixed?
Thank you all for your help so far.