Under the Template Settings page, if you set up the "Source Page Whitelist" under the online signing link, means only under the URL you entered as whitelist will be able to open up this online waiver.
If you see this "page not found" after clicking the online link of your waiver, please go to the "Template Settings -Online Signing" page to check if you entered any URL under the " Source Page Whitelist".
If you want everyone under any page to be able to open the online link of your waiver, you need to clear up the URLs in the "Source Page Whitelist".