Hi,
My command line for creating maps (depending the case) is something like:
osmosis --rx file=country.osm --s --mw file=country.map type=hd bbox=minLat,minLon,maxLat,maxLon map-start-position=lat,lon map-start-zoom=zoom preferred-language=language tag-conf-file=tag-mapping.xml
I never had problems with the languages.
If you are sure that your tags are correct, may be you need to check
the min/max zoom values at both the tag-mapping and render theme you use.
Best regards, Emux
https://play.google.com/store/apps/details?id=gr.talent.cruiser