You attempt to connect to a virtual desktop from the internet with the VMware View Horizon Client which passes the traffic to VMware Horizon View Security server which then contacts the View Connection server which then attempts to establish a connection to the VDI but fails with the following message:
The display protocol for this desktop is currently not available. Please contact your system administrator.
While there are various reasons why this error would be thrown, one of them is if your View Connection server has a stale DNS entry to the virtual desktop. A client recently contacted me to troubleshoot this error message and what the problem ended up to be was that the virtual desktops were changed to another port group and while the DNS entries were updated on the domain controllers in the same Active Directory site, the View Connection servers were using DNS servers from a different Active Directory Site so the changes to the DNS entries were not immediately available causing this error to be thrown.