InnoSetup Language not shown up

Some languages are missing on the Select Setup Language dialog, or it doesn't show up at all.
If you would like to force all languages to be visible regardless of whether they can be displayed properly under the active code page, set the ShowUndisplayableLanguages [Setup] section directive (new in Inno Setup 5.1.7).
ShowUndisplayableLanguages=yes
refer to here.