This plugin is not properly prepared for localization

I would like to translate the few strings of this plugin into spanish, but as you can see at https://translate.wordpress.org/projects/wp-plugins/easy-theme-and-plugin-upgrades/

This plugin is not properly prepared for localization (View detailed logs on Slack). If you would like to translate this plugin, please contact the author.

Regards.

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