I don't think Marvin has changed nearly as much as Calibre. You should probably ask this question in the Calibre forum...it could be that Philantrop hasn't updated MarvinXD lately??
Sorry I couldn't offer more help.
Edit:
I just looked over at the Calibre/Plugins/MarvinXD thread
here. It looks Like Philantrop has been very ill for a while and hasn't been able to keep up with the plugin. But perhaps someone over there can give you an idea?
Cheers,