What’s your user flow? Do you want a user to go to checkout or the cart after clicking the ATC button? I can add to cart (ATC) but the icons are not clear for an eCommerce site in the header. I would never know that if I click the one button I am taken to checkout. It’s just a plus sign.
I’d suggest changing that to a cart icon so it’s clear.
If you want the user to automatically be taken to the checkout page after clicking the ATC you’ll have to write a hook, if you want the user to be taken to the cart after clicking the ATC you can go to WooCommerce > Settings > Products and then check the box that says “Redirect to the cart page after successful addition”
For a hook to the checkout page you’ll add this script to your child theme’s function file
add_filter( 'woocommerce_add_to_cart_redirect', 'custom_redirect_checkout_add_cart' );
function custom_redirect_checkout_add_cart() {
return wc_get_checkout_url();
}