I fixed the scene in order to work with the latest mitsuba exporter
Here is the file: new monster plastic mitsuba.blend (3.25 MB)
And here is the rendered image:
so what is the difference between new and old mitsuba exporter?
The difference is that the new exporter uses a node based material system, also has some changes in light settings and was not compatible with the previous versions in order the settings of a scene to appear correctly.