echo get_theme_mod not showing on live website

Hi,

I created an option for my site customization

$wp_customize->add_setting( 'sub_title', array(
        'type' => 'theme_mod',
        'default' => __( 'Laissez-vous guider par la soif d\'aventures et la découverte du monde', 'aurora' ),
        'sanitize_callback' => $pgwp_sanitize
    ));

And on my page I have

<div class="page-title home-title"> 
        <h1><?php bloginfo( 'description' ); ?></h1> 
        <h2><?php echo get_theme_mod( 'sub_title' ); ?></h2> 
    </div>   

However, I really don’t understand, because when editing in the live editor, I can see the change of the sub_title, but when publishing and viewing from the main website, I can’t see it…

https://i.postimg.cc/Y0gHSpkJ/Capture-d-cran-2021-05-09-160028.png
https://i.postimg.cc/kX3Cptv9/Capture-d-cran-2021-05-09-160053.png

What’s wrong?