prlctl command executed for the specific container using the CT name fails with the following error - in this example it is CT #1234 with the name "ct-1234":
~# vzlist 1234 -o ctid,numproc,status,ip,name CTID NPROC STATUS IP_ADDR NAME 1234 - stopped - ct-1234 ~# prlctl list ct-1234 Failed to get VM config: The virtual machine could not be found. The virtual machine is not registered in the virtual machine directory on this server. Contact your Parallels Server administrator for assistance.
The name of the container in the question is absent in the file
/etc/parallels/vmdirectorylist.xml, which contains information about all registered and known containers and virtual machines.
One of the possible reasons for such issue is managing the container by
vzctl tool while the service of Parallels Dispatcher is stopped.
It is necessary to change container's name to any other and change it back, for example for the CT #1234:
~# UUID=$(prlctl list -Ho uuid --vmtype ct 1234) ~# prlctl set $UUID --name ct-1234.orig ~# prlctl set $UUID --name ct-1234