404/failure to send error messages

Hello, my client told me when she filled out my contact us form she was redirected to a 404/"failure to send" page. So she filled out the form again and got the same error.  However, I received both of the forms she filled out.  What's happening and how can I fix this so other people don't experience this too?

Thanks,
Julie

You have the following page as your custom Thank you URL and it doesn't exist in your website:

https://www.yourpetsnanny.com/Home_Page.html

You may consider changing this URL. Here's how to change it: http://www.jotform.com/help/38-Redirecting-Users-to-a-Different-Page. OR, use our default thank you page.

D'oh!  Thanks you Welvin!