Add this code to your functions.php file to enable Divi Builder on CPTs

mindsize-product-description-et-builder.php

/********This function is used to display the pagebuilder option on the CPTs**********/
add_filter('et_builder_post_types', 'mndsz_divi_admin_display_pagebuilder');

function mndsz_divi_admin_display_pagebuilder($mndsz_post_types)
{
    $mndsz_get_custom_post_types = get_post_types(array('public' => true, '_builtin' => false));
    $new_post_types = array_merge($mndsz_post_types, $mndsz_get_custom_post_types);

    return $new_post_types;
}