[PVE-User] IS able to login through web interface, but the status of the VM is marked as ??

[Joseph John]

Dear All ,
We are using PVE 8.X EE , we have 8 node cluster
today one of the  cluster , we were able to login through the web
interface, but the status of the VM machines were marked as ?
We tried to login in using SSH, were able not able to  init 6 , it was
showing the message

root at pve-4:~# init 6

*Failed to set wall message, ignoring: Transport endpoint is not
connectedCall to Reboot failed: Transport endpoint is not connected*

Later on we did hard reset and the system was back
How could we know what was the problem?, which log files  should we use? to
understand the issue

Advice requested


Thanks
Joseph John