This answer explains why the SSL certificate is not valid for Plesk/Virtuozzo.
When you connect to Plesk or Virtuozzo control panel, you will get an error saying the certificate is invalid.
This is because both Plesk (8443) and Virtuozzo (4643) ports are forwarded through Service-VPS and therefore the certificate shows the IP address for the Service-VPS.
Unfortunately there is no way to change this on the VPS but this is normal for a VPS and should not impose any problems with the running of the VPS.