What is JotForm?
JotForm is a free online form builder which helps you create online forms without writing a single line of code. No sign-up required.
At JotForm, we want to make sure that you’re getting the online form builder help that you need. Our friendly customer support team is available 24/7.
We believe that if one user has a question, there could be more users who may have the same question. This is why many of our support forum threads are public and available to be searched and viewed. If you’d like help immediately, feel free to search for a similar question, or submit your question or concern.
Are you trying to use the "Test" keys payment details? (Credit Card Number: 4242424242424242 / CVC : 123)
If yes, then the test mode should be enabled.
If you are not using the "Test" keys, and you got that error, it means that the credit card information is invalid. Please try another credit card information.
Also, it'll be helpful if you can provide a screenshot of the exact error message you're getting and when does it appear.