Error occurs when a Persistent Chat Server pool is down even if you're not using that pool in Skype for Business 2016

Symptoms

You receive an error message that states that your connection with the Persistent Chat Server pool is down in Microsoft Skype for Business 2016. This issue occurs even though you're not using that pool.

Resolution

To fix this issue, install the March 5, 2019, update (KB4462190) for Skype for Business 2016.

Note After applying this update, you can use one of the following options to disable the banner that is shown when the Persistent Chat server is down.

• You can create a Group Policy Object (GPO) to add a new DWORD registry key EnablePersistentChatPoolDown and set the value to 0 in any one of these registry paths:
  HKEY_CURRENT_USER\SOFTWARE\Policies\Microsoft\Office\16.0\Lync
  

  or
  HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Office\16.0\Lync

• Alternatively, you can create a custom policy entry and add it to the client policy:
  $x = New-CsClientPolicyEntry -Name "EnablePersistentChatPoolDown" -Value "false"

  Set-CsClientPolicy -Identity "<ClientPolicyName>" -PolicyEntry @{Add=$x}