Dell - Microsoft Hyper-V Manager - Ceases to function within seven days of a server reboot

Hello,

Server = Dell PowerEdge T620

Operating System = Windows Server 2012 (Version 6.2, Build 9200, 64 bit)

This server functions as a physical host for three Virtual Machines.  Each VM is running Windows SErver 2008 R2.

Within seven days of rebooting the physical host (T620), the Hyper-V Manager no longer functions properly.  The computer name of the host is no longer listed in the Hyper-V Manager, and thus the computer names of the Virtual Machines are no longer listed in the Hyper-V Manager.

Please help.

Thank you.