Is anyone else having this problem? I checked everything and it is all current through my bank and accounts but the payment says it fails every time I try.
Matt, you can login into Zwift through their web site and configure payment using your credit card, instead of iTunes. Many people complained of issues with iTunes, many issues are with a small gap between the time when Zwift considers payment due and when iTunes actually provides it to Zwift.
It is the same Zwift account regardless of which platform you use to run it, so you can cancel your iTunes payments and go with direct payment to Zwift via credit card.