Form Confirmation URL isn't working


I created a page with a form. In the edit section I put a thank you page as a form confirmation URL.

The issue is that when the user completes the form and press the button to validate, it redirects him to an incorrect URL.

For example, the URL confirmation dialogue is :
But Unbounce redirects the user to this URL which doesn’t exist :

What can I do in order to fix this problem?

Thanks !

I used it on a test page / test contact form and it worked fine.