We have a new MSP HaaS Client we are deploying and we are also having a blank black screen. The server is Windows Server 2016 Essential running on a VMware ESXi 5.5 host. The LabVNC although slow does work. We were also able the view the console via the VMware console and was able to verify Screenconnect tools (send ctrl+alt+del, restart, file transfer) work but you just have a blank screen so you can't see it.
If anyone finds a solution please share.
Customer support service by UserEcho