Lute uses MeCab to parse Japanese, so MeCab needs to be
installed on your machine (see notes
in the manual).
Lute includes the Python
library natto-py
to interact with MeCab. natto-py can usually find MeCab
automatically, but you may need to set the MECAB_PATH, per
the manual.
Try different values for MECAB_PATH, including leaving
the field blank, until clicking the "test"
button returns a "success" message.