Symptoms
Note: This is a scenario specific to the precise Log Lines highlighted below, for General Troubleshooting Steps , please refer to Troubleshooting Agent Unreachable status in VMware Horizon (2083535)

Note: This scenario will typically impact Horizon Manual or Full Clone Pools.
If the Operating System has also been updated - Please refer to Upgrade Requirements for Windows 10 Operating Systems (2148176)

Please ensure your new version of horizon agent is compatible with your current version of esxi and the version of tools as a sanity measure:
https://www.vmware.com/resources/compatibility/sim/interop_matrix.php
  • After reinstalling or upgrading the agent, the View desktop reports this message on the View Administrator console:

    Agent Unreachable
     
  • In the Horizon Agent log, you see message similar to:

    <YYYY-MM-DD>T<time> 789-07:00 DEBUG (0EB8-0F74) <theTopicMessageManager> [AgentJmsConfig] Published CHANGEKEY request

    </time>
    After approximately 10 seconds, you see this entry:

    <YYYY-MM-DD>T<time></time> 789-07:00 DEBUG (0EB8-0F74) <theTopicMessageManager> [AgentJmsConfig] Timeout waiting for success response

    Note: You see entries similar to in the same log file:
    • update rejected, attempt to reconfigure as paired with missing key information
    • FATAL (0324-23C) <572> []The JVM has exited with code 6.
    • INFO (0308-052C) <JavaBridge> wsnm_jms died, restarting in a minute
       
  • In the Connection Server log, you see the entries similar to:

    <DesktopControlJMS> [JMSMessageSecurity] Message could not be validated: Signature invalid for identity agent
    <DesktopControlJMS> [DesktopTracker] CHANGEKEY message from agent/<Agent GUID> is discarded as it cannot be validated
 
Note: The preceding log excerpts are only examples. Date, time, and environmental variables may vary depending on your environment.


For more information on the location of the log files, see Location of VMware View log files (1027744).
 
 Cause
This issue occurs if the process of changing the key in the Connection Server configuration fails and, therefore, causes the communication between the View Agent and Connection Server to break.

When the View Agent is reinstalled or upgraded, it may change the key pair used to identify the View Agent with the Connection Server.

 
 
 Resolution
This matter has been resolved in code in Horizon 7.10 and higher :
https://docs.vmware.com/en/VMware-Horizon-7/7.10/rn/horizon-710-view-release-notes.html#resolvedissues
2382522: After an upgrade to Horizon 7.4 or later, virtual desktop machines appear to be in agent unreachable state after restarting Connection Server.
2258649: After you upgrade Horizon Agent to version 7.4 or later, the RDS host status appears to be in the agent unreachable state.

If you encounter this issue on a previous release , please find the below workaround.

To resolve the issue, perform below steps:
  1. In the View Administrator console, on the left pane navigate to View ConfigurationGlobal Settings.
  2. Under Security, click Edit - Ensure that the Message security mode is set to Enabled in View admin UI.
  3. Run the command from this location on a connection broker :
C:\Program Files\VMware\VMware View\Server\tools\bin

vdmadmin -A -d desktop-pool-name -m name-of-machine-in-pool -resetkey

Note : To run the above command, open Command Prompt as Admin by selecting "Run as Administrator".
  1. Restart the virtual desktop on which the command was issued.
Note:
  1. For resetkey to appear in vdmadmin set the key ToolsSupportLevel to 60 by navigating to HKEY_LOCAL_MACHINE\SOFTWARE\VMware, Inc.\VMware VDM ([HKLM\Software\VMware, Inc.\VMware VDM]ToolsSupportLevel=dword:60)
  2. This workaround does not apply for View unregistered desktops.