LSASS.EXE locks up and does not process authentication requests in Skype for Business clients

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Skype for Business 2016 Skype for Business 2015 Microsoft Lync 2013 Windows 10 More...Less

Symptoms

When you use Microsoft Skype for Business clients in Windows Server 2012 R2, you may experience authentication failures.

Cause

This issue occurs because of a deadlock in Windows Local Security Authority Subsystem Service (LSASS) in Windows Server 2012 R2. The deadlock causes perceived lockup of the server in which all incoming server-to-server TLS negotiations fail and authentication requests from Skype for Business clients fail.