did you changed the language in the wp-config.php to french? Then you have to create also a language file for french (take the sevenleague as basis for the new file). If you want to translate only the “all” text, it’s better you change only the “all” text in the sevenleague.po file and dont change the wp-config.php, then you don’t have to translate all the things in the language file.
The plugin description says that it is not working with every template
Oh, ok, we’ve tested the plugin with the portfolio function in our themes and it worked fine.
Maybe you can work with this, another client of us is using this plugin: