Wrong text domain

I trying to add the new way to translate plugin to DNUI, but i get this

This plugin is not properly prepared for localization. If you would like to translate this plugin, please contact the author.

I already add the Text Domain in the readme.txt like this

Author URI: https://www.nicearma.com/
Text Domain: dnui
Domain Path: /languages

All text have the ‘dnui’ like this

<?php _e('WARNING ABOUT THIS PLUGIN', 'dnui') ?>

But i’m getting

This plugin has a wrong text domain declaration in the file header:
./dnui.php: Text Domain: dnui
Code for dev was processed.
Readme for dev (dnui-delete-not-used-image-wordpress/trunk/) in process…

I don’t know why i’m getting this error and how to fix it. Maybe is because i have

Plugin Name: DNUI (Delete not used images)

and not

Plugin Name: DNUI

To complete the info, i use the Slug dnui

You can find the principal php file here