Veeam ONE uses TLS to ensure secure data communication between Veeam ONE Reporter and Veeam ONE Business View websites and a web browser.
When you install Veeam ONE, you can generate or choose a self-signed certificate. In this case, when you try to access Veeam ONE Reporter or Veeam ONE Business View from a remote machine, the browser will display a warning notifying that the connection is untrusted (although it is secured with TLS).
To eliminate the warning, import the self-signed certificate to client machines (the machines from which you plan to access the Veeam ONE Reporter and Business View websites).
For details on importing TLS certificates, see this Microsoft KB article.