Doesn’t recognize string added via custom setting

Hi,

I’m trying to translate my main website title, but I’m unable to do it. I’ve create custom settings for my page.

Code used in functions.php

function aurora_customize_register( $wp_customize ) {
    // Do stuff with $wp_customize, the WP_Customize_Manager object.

    /* Pinegrow generated Customizer Controls Begin */
    $pgwp_sanitize = function_exists('pgwp_sanitize_placeholder') ? 'pgwp_sanitize_placeholder' : null;

    $wp_customize->add_section( 'aurora_default_cs', array('title' => 'Personnalisation de la page d\'accueil'));

    $wp_customize->add_setting( 'home_img', array(
        'type' => 'theme_mod',
        'sanitize_callback' => $pgwp_sanitize
    ));

    $wp_customize->add_control( new WP_Customize_Media_Control( $wp_customize, 'home_img', array(
        'label' => __( 'Image de l\'accueil', 'aurora' ),
        'type' => 'media',
        'mime_type' => 'image',
        'section' => 'aurora_default_cs'
    ) ) );

    $wp_customize->add_setting( 'home_vid', array(
        'type' => 'theme_mod',
        'sanitize_callback' => $pgwp_sanitize
    ));
    $wp_customize->add_control( new WP_Customize_Media_Control( $wp_customize, 'home_vid', array(
        'label' => __( 'Home video', 'aurora' ),
        'type' => 'media',
        'mime_type' => 'video',
        'section' => 'aurora_default_cs'
    ) ) );
    function allow_video_upload( $existing_mimes ) {
        $existing_mimes['mp4'] = 'video/mp4';
        $existing_mimes['mov'] = 'video/quicktime';
        // Ajoutez d'autres extensions de fichiers vidéo si nécessaire
        return $existing_mimes;
     }
     add_filter( 'mime_types', 'allow_video_upload' );
    
     $wp_customize->add_setting( 'main_title', array(
        'type' => 'theme_mod',
        'default' => '',
        'sanitize_callback' => $pgwp_sanitize
    ));

    $wp_customize->add_control( 'main_title', array(
        'label' => __( 'Titre principal', 'aurora' ),
        'type' => 'text',
        'section' => 'aurora_default_cs'
    ));

    $wp_customize->add_setting( 'sub_title', array(
        'type' => 'theme_mod',
        'default' => '',
        'sanitize_callback' => $pgwp_sanitize
    ));

    $wp_customize->add_control( 'sub_title', array(
        'label' => __( 'Sous-titre', 'aurora' ),
        'type' => 'text',
        'section' => 'aurora_default_cs'
    ));


}
function register_theme_strings() {
    pll_register_string('aurora', get_theme_mod('main_title'), 'aurora', true);
    pll_register_string('aurora', get_theme_mod('sub_title'), 'aurora', true);
}
add_action('init', 'register_theme_strings');

And in my front-page.php

$main_title = get_theme_mod( 'main_title' );
$sub_title = get_theme_mod( 'sub_title' );

 <div class="home-title"> 
            <h1><?php pll_e($main_title); ?></h1> 
            <h2><?php pll_e($sub_title); ?></h2> 
        </div>             

Any idea how it can recognize that?