Skype for Business client stops responding when receiving a toast notification of an IM or an incoming call in Citrix VDI environment


Assume that you use the Microsoft Skype for Business client in a Citrix VDI environment that has HDX RealTime Optimization Pack (RTOP) Connector installed. When you run one or more Lync SDK-based applications and receive a toast notification of an instant messaging (IM) message or an incoming call, the client stops responding.



Follow the steps in this section carefully. Serious problems might occur if you modify the registry incorrectly. Before you modify it, back up the registry for restoration in case problems occur.

To fix this issue, install the April 2, 2019 update for Skype for Business for a Click-to-Run installation. To do this, open an Office program, such as Word, and then select File > Account > Update Options > Update Now.


If "Update Options" does not exist in the client, this is an .msi installation.

Screenshot that shows the Update Now tab selected in the Update Options.

Don't see your Skype for Business client in the list? Click here for a complete list of clients. You can download the Click-to-Run client from the Office365 Portal.

After you apply the update, create a Group Policy to set the following registry key on clients:

Subkey: HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\16.0\Lync

Value: EnableDelayPostingOfDeferredCOMEvents

DWORD data: 1
A lternatively, you can enable this fix by creating a custom policy entry and adding it to the client policy, as follows:

$x = New-CsClientPolicyEntry -Name "EnableDelayPostingOfDeferredCOMEvents" -Value "true"
Set-CsClientPolicy -Identity "<ClientPolicyName>" -PolicyEntry @{Add=$x}

Lync 2013 was upgraded to Skype for Business in April 2015.

Third-party information disclaimer

The third-party products that this article discusses are manufactured by companies that are independent of Microsoft. Microsoft makes no warranty, implied or otherwise, about the performance or reliability of these products.

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