Julia-promocodes

[tranquil marlin]

@dense light note that you can't use promo codes that would make the amount either $0 or below our minimum charge amount (https://stripe.com/docs/currencies#minimum-and-maximum-charge-amounts)

at least in one-time payment mode; it is supported for subscriptions

so if you try to use a promo code that would reduce the amount that much, it's rejected

that's almost certainly what you're seeing, unfortunately!