Divi by Elegant Themes is a WordPress theme with a catch: You can't pinch zoom your website. This is not in accordance with WCAG standards, but you can change it very easily with this quick snippet for your child theme's functions.php.

Viewport Meta Tag für Divi überschreiben – change user-scalable in Divi

function nxt_remove_et_viewport_meta() {
	remove_action('wp_head', 'et_add_viewport_meta');
}
add_action('after_setup_theme', 'nxt_remove_et_viewport_meta');

function nxt_enable_zoom() {
	echo '<meta name="viewport" content="width=device-width, user-scalable=yes, initial-scale=1.0, minimum-scale=0.1, maximum-scale=10.0">';
}
add_action('wp_head', 'nxt_enable_zoom');