What do I do when receiving the following message: "Metadata not defined"?

Thanks for reaching out to the Community, @danny13.

I'd like to help you with the message that you're receiving in QuickBooks Online when you try to process a credit card payment.

I'm going to start this process by isolating the issue and see if this caused by the stored data in your browser. We can isolate the issue by opening an Incognito Window or Private window in your browser. Here's how:

• Press Ctrl + Shift + P for Internet Explorer or Firefox.
• Press Ctrl + Shift + N for Chrome.
• Hold down Command + Shift + N for Safari.

If this works, then we'll have to clear your cache in your browser. This will erase the data stored and prevents unusual behavior in the future.

In case you need to enter a delayed credit, you'll want to check out this article: Enter and apply credit memos and delayed credits in QuickBooks Online.

Let me know if this worked for you! Have a great day.