There are currently no logon servers available to service the logon request when I login on VM with VDI configuration

Dear,

I had Domain server and server 2012 with Hyper-V role installed,

and I configured VDI on it, every think it was working, but suddenly when I tried to login to the my VM by used VDI, thin client , I couldn't, and I received the following error:

"There are currently no logon servers available to service the logon request"

Also, Also, I couldn't access the VM's when from the Server directly and I received the same error.

Please advice .