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.
How can I fix the 'Not Found' error?Asked by jrowley on January 18, 2016 at 06:12 PM
When people submit a jotform, it shows them an error saying that the page isn't found. We receive the jotform, but the clients don't realize it. Please help us fix this error. Thanks.
I think you have figured this out already. The error is related to your custom thank you page URL which doesn't exist your website;
If you want to use a thank you page, make sure to create it first to your website.