The non-English menus have never been supported in the Cool VL Viewer, even if, as a result of the now abandoned overlay package distribution method, it was still possible to use the deprecated (never updated) translations from Snowglobe.
Please, see the
release notes in the announcement forum.
If some people can provide me with proper, up to date translated XML menus for some languages, then I might include them in future Cool VL Viewer releases, but I can't afford spending time myself on these (not to mention that I don't know any other language than French and English).