There is a compatibility issue with your plugin and WooCommerce Coupon Restrictions. Location Restrictions are ignored on Cart and Checkout.
When I add a product to the cart the coupon is applied without first checking coupon restrictions.
When I visit the cart I see the coupon and when I go to checkout I see the coupon, Address is completely empty so I think this is an error. Cart and Checkout should not apply coupon until a shipping address is added. Woocommerce Coupon Restriction is based on Location Country(United States(US)) and State(CA).
If address is empty coupon should not apply due to restriction set by Woocommerce Coupon Restriction.