Can't schedule or join a meeting after you apply May 2017 Cumulative Update for Skype for Business Server 2015

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Applies To

Skype for Business Server 2015

Symptoms

Consider the following scenario:

You apply May 2017 Cumulative Update for Microsoft Skype for Business Server 2015.
The version of .Net Framework that's installed on the Skype for Business Server 2015 Front-End Server is less than 4.6.2.
You enable the System cryptography: Use FIPS compliant algorithms for encryption, hashing, and signing security setting on the Front-end Server.

In this scenario, you can't schedule or join a meeting by using the Meet Now option or Outlook Skype Meeting add-in.

Cause

This issue occurs because Meeting functionality dependency: SHA256 Managed implementation is incompatible with Federal Information Processing Standard (FIPS) guidelines in Cumulative Update 5.