Clicking the link to a database from the Heroku Dashboard shows a "not found" error.
We sometimes see this when there are multiple Heroku accounts in use on one browser session, or when the browser session has become invalid in some other way.
To resolve this issue we recommend logging into the Heroku Dashboard from a private browsing window and following the links from there. This should help to rule out any issues with your current browser session. If that fixes things then restarting your browser should resolve the issue.