Hello there, tfva.
In addition to what Fiat Lux - ASIA provided, missing information or authorization issues can cause the decline of the customer's credit card. Here's an article that will give you a few ways to check if you enter the credit card info manually.
If everything has been set up and entered correctly and the same thing happens, you can ask them to use a different mode of payment or get in touch with our Phone Support Team so we can securely help you through it.
You can refer to this link that lists all articles that will help you in processing customer payments: QuickBooks Payments FAQ.
Feel free to mention me in your reply if there's anything else that you need help with. You take care always and have a great day!
