Server 2012 R2 RDS does not display connections to one Host, will not redirect WAN users to the other

Question

I've recently discovered an issue on our RDS environment where Server Manager on our RD Gateway server does not display active connections to the one of the Session Hosts in the collection. In that collection are 2 Session Hosts, A and B. All the Remote Desktop connections to B appear, but none of the RD connections to A appear, despite the fact I can confirm there are 25 users actively connected to and using that Session Host, and they got there via the RD Gateway.

I've looked at the following articles on this issue:

• https://social.technet.microsoft.com/Forums/windowsserver/en-US/f7ae2876-0887-467d-bf38-ef8eb3066658/rds-gateway-manager-shows-no-connections?forum=winserverTS
• Remote Desktop Gateway MMC not showing some connections under "Monitoring"

I feel I've ruled out RD Connection Authorization Policy and Resource Authorization Policy issues, and I haven't changed anything about the collection's configuration. I haven't had much luck finding any other articles describing these symptoms.

Edit: Since posting this issue, I have a new finding:

• Since implementing an IPSec tunnel to send internet traffic on Session Host B thru our new web filtering/security provider, all of our WAN users were failing to be redirected to Session Host B when appropriate for load balancing. They were all winding up on Session Host A (whose connections do not appear in the Server Manager on RD Gateway). Users on the same subnet as the RD Servers were still subject to redirection but wound up on Session Host B, probably due to load balancing. I discovered this problem when I tried to implement the tunnel on Session Host A, and wound up disconnecting our remote users. The disconnection was remedied by adjusting the port ranges (changed from any to 80-443) going thru the tunnel. There's still an issue with redirection failing for WAN users, but at least my users can connect again.

Solution

This issue has since been resolved thanks to a call to Microsoft Support. The networking situation was a red herring. MS Support solved the issue by removing the Session Host A (the affected host) from the Collection, uninstalling the Session Host role from the computer, and rebooting, then reinstalling the role, and adding it back to the Collection. Don't know why I didn't think to do that myself, and am still in the dark as to what caused it, but hopefully this will help someone who runs into a similar issue.