Edit `src/main/resources/fess_config.properties`:

Find the `supported.languages` property (around line 202) and ensure your language code is included:

```properties
supported.languages=ar,bg,bn,ca,ckb_IQ,cs,da,de,el,en_IE,en,es,et,eu,fa,fi,fr,gl,gu,he,hi,hr,hu,hy,id,it,ja,ko,lt,lv,mk,ml,nl,no,pa,pl,pt_BR,pt,ro,ru,si,sq,sv,ta,te,th,tl,tr,uk,ur,vi,zh_CN,zh_TW,zh
```

**Optional configurations:**

    protected static Map<String, Map<String, FieldAnalyzerMapping>> fieldAnalyzerMappingMap = new ConcurrentHashMap<>();

    /** Supported languages. */
    protected static final String[] SUPPORTED_LANGUAGES = { "ar", "bg", "bn", "ca", "cs", "da", "de", "el", "en", "es", "et", "fa", "fi",
            "fr", "gu", "he", "hi", "hr", "hu", "id", "it", "ja", "ko", "lt", "lv", "mk", "ml", "nl", "no", "pa", "pl", "pt", "ro", "ru",