Remote Desktop Authentication Error Has Occurred. The function requested is not supported. CredSSP.

To fix the Remote Desktop Authentication Error Has Occurred. The function requested is not supported. CredSSP error, Login to server using VNC/KVM or console. Start >> Computer >> Properties >> Remote desktop setting and uncheck the box Allow connections only from computers running remote Remote desktop running with Network Layer Authentication.
And try to login to RDP again.

Regards.