The issue you’ll find is that the coupon code is a separate form. Once you add it to woocommerce_review_order_before_payment, it will be inside the checkout form. This means that the “Apply Coupon” button will submit the order form instead of applying the coupon. I’m dealing with the same issue. I recommend creating a modal to input the coupon so it doesn’t nest a form inside a form.
Wordpress Multisite Version 4.9.8
Arconix FAQ Version 1.8.2
Logging in as a Super Admin to a child site dashboard resulted in a redirect loop.
