Let's Encrypt SSL can not be installed to secure Plesk in Tools & Settings > SSL/TLS Certificates > Let's Encrypt:
PLESK_ERROR: Error: Could not issue Let's Encrypt SSL / TLS certificate for server.localdomain .
Invalid response from https://acme-v01.api.letsencrypt.org/acme/new-authz.
Type: urn: acme: error: malformed
Detail: Error creating new authz :: Name does not end in a public suffix
Server hostname is not a fully qualified domain name (FQDN).
Change server name to a fully qualified domain name:
- Login to Plesk
- Go Tools & Settings > Server Settings and set the FQDN hostname (e.g., example.com) that will be used for accessing Plesk into the field Full hostname and click OK to apply changes.
Note: In order to secure Plesk with the Let's Encrypt certificate, server's hostname must resolve to the Plesk server IP address.