The above error message can be seen when trying to connect to a virtual machine from the Hyper-V console on the Hyper-V host.
The reason for this is that the self signed Hyper-V machine management service certificate has expired, this is the certificate issued to itself for authentication when Hyper-V role is installed on the server.
The workaround for this is to: Shut down all VM’s, restart the Hyper-V VMMS, start the virtual machines again. This renews the self signed certificate for another year. However a better resolution is to install the following handy-dandy, super duper Microsoft KB! By doing so this will in the future auto-magically update the Hyper-V VMMS certificate………
Hope this helps!