PARTIALLY SOLVED
I’ve an update! The billing state dropdown retrieves the state, from the user profile, if I disable the filter “default_checkout_billing_state” within Woocommerce-checkout-manager.php. To avoid modification to the source code (overwritten on next update) I’ve disable the filter from the function.php, of my child theme, adding the following code:
add_action( 'init', 'remove_wooCheckout_filters' );
function remove_wooCheckout_filters(){ //Have to do it after theme setup, because child theme functions are loaded first
remove_filter('default_checkout_billing_state', 'wooccm_state_default_switch');
}
I hope the developer will help me to debug or find a more elegant solution. Have a good day.
