It looks like the C3D file is missing information, which is supposed to always be in the file.
In the forceplate file line 102 there is this line
#var AnyInt ZERO = reshape(C3D_OBJECT.Groups.FORCE_PLATFORM.ZERO.Data, {2});
Which means that the script will look for the variable "C3D_OBJECT.Groups.FORCE_PLATFORM.ZERO.Data" which does not exist in your file.
I have search the file and i actually do not see "ZERO" being used for anything, so i think you can simply out comment this one line, and it would load.