Apple pay

I like to use Apple Pay when checking out online. Unfortunately, on any website I have ever seen, it only shows up for express checkout. If I have a coupon code, I have to go through the regular checkout but then the Apple Pay option is no longer available. Is there something I'm doing wrong? I've had too many issues with PayPal so I'd rather use Apple but it's frustrating that I can't use it if I have a coupon to apply. Thanks.