Apple‘s new iPhone 13 family went up for pre-order Friday morning at 8 a.m. ET Since then, customers have had trouble buying new smartphones using their Apple Card. Enough customers are having trouble that it quickly became one of the top trending topics on Twitter.

Apple Card, which allows users to purchase Apple products and receive up to 3% cashback was launched in 2019. Apple’s greatest fans use it, so many are trying to place orders for the new iPhone before it launches next week.

Apple’s iPhone 13 Pro is starting to ship in October. That was a week before the launch date of Sept. 24, when Apple launched its more expensive models.

If they have another credit card, shoppers can still purchase the iPhones. Apple’s own payment system isn’t functioning on Apple’s biggest launch day.

Sometimes the systems are overloaded, and these problems can be quickly resolved. But the problem seems to still exist an hour after the iPhones go on sale.

Apple spokespeople were unavailable for comment immediately.