Parallels Virtualization and Automation Software

SYMPTOMS

After VZU35123 , VZU35125  Virtuozzo updates, users trying to access Plesk by the fully qualified domain name (FQDN) (e.g. https://domain.com:8443 ), are able to login and see the left frame, but the right frame returns
 
“Service Unavailable: Service is not available now, probably your Plesk is mis-configured. Contact Your provider for details.”

or

"Plesk Diagnostics"


When accessing Plesk by ip address (e.g. https://IP_address:8443 ), it works properly.  The domain is resolvable and the website itself can be accessed from the outside.

CAUSE

By default, Plesk installations get name resolution from the service virtual environment (SVE). The above referenced Virtuozzo updates change certain characteristics of the SVE that affect the ability to connect to the DNS ports if the SVE is configured in “NAT mode”. As a consequence, domain names cannot be resolved and Plesk’s right frame is not shown.
I.e. if SVE is running with internal IP (in NAT mode) it cannot reach DNS with public IP.

RESOLUTION

Either reconfigure the SVE with public IP ( without "NAT Mode” )  or point all Plesk VEs to an available internal DNS server.