A 404 page means that the server could not find the page at the path listed in the browser's address bar. There are many different reasons why a "published" page might return a 404 to a visitor including:
Domain name server (DNS) outages, new DNS records, or improperly configured DNS settings.
Redirects on the original page that lead to a page that can't be found.
A change in the page's original URL without a proper redirect.
Improperly configured internal DNS records.
Broken query parameters from external tracking tools.
If you are unable to access the page after confirming the above configurations are correct, contact HubSpot Support.