Are you getting any error messages when making payments through credit card in QuickBooks Online (QBO)? Any additional information will help me provide the best resolution.
In the meantime, try signing into your QBO using a private browser (incognito). There are times that the browser is already full of frequently accessed page resources, causing some unusual responses.
Here's how:
Press Ctrl + Shift + N (Google Chrome).
Ctrl + Shift + P (Firefox).
Control + Option + P (Safari).
Once logged in, try to enter the payment again to double-check. You can also visit this article for more information: Record your payments to credit cards.
If it's successful, return to your default browser and perform a clear cache to refresh the system. However, if the issue persists, try using other supported browsers.
Please know that I'm only a few clicks away if you have any additional concerns. I'll be here to assist. Have a good one!