Warning in browser is shown whenever the domain with installed Let's Encrypt SSL is accessed with www-prefix like
CONFIG_TEXT: Your connection is not private
This server could not prove that it is www.example.com; its security certificate is from example.com. This may be caused by a misconfiguration or an attacker intercepting your connection.
The certificate was issued only for the domain
example.com, without www-prefix.
Reissue certificate with www-prefix:
- Login to Plesk;
- Open Domains > example.com > Let's Encrypt;
- Check the option Include a "www" subdomain for the domain and each selected alias;
- Click Renew.