Translated my theme (translation not showing up)

Question

I read a lot about what is the optimal to translate your website (french and english in my case)

I set up a Multi site where I created two site one french mywebsite.com/fr and one in english mywebsite.com/en

I am now in the process of translating my theme(in french by default) I added this to my theme function.php:

load_theme_textdomain('INTERluminaires', get_template_directory() . '/languages');

then modified my template files in order to be able to translate some text

<?php _e("Design et conseils", "INTERluminaires"); ?>

created a po and mo file with poedit, everything goes well.

I uploaded those files in my theme folder /languages

those files are named en_CA.po and en_CA.mo (I tried INTERluminaires-en_ca.po and mo to no avail)

when I change my theme language in settings general and refresh my website nothing is translated.

any idea what could be wrong here?

btw I managed to translate a plugin I installed without any problem.