Coupons are not being applied to a transaction

If your checkout is looking good with a coupon applied but the charge was full price in Stripe take a look at your server caching setup. 

1. In one case Cloudflare was bringing back an old ?query value back from the cache
2. The other thing may need to be done was to exclude the coupons cookie from Varnish on the server

Once that has been corrected go back and re-enable the the server cache and the site cache to make sure they don't interfere.