Consider the following scenario:
You run the Set-CsPlatformServiceSettings cmdlet to set the value of the enableExternalAccessCheck parameter to true in Microsoft Skype for Business Server 2015.
You run the Set-CsExternalAccessPolicy cmdlet to set the value of the EnableOutsideAccess parameter to false per user.
In this scenario, when you try to sign in to Unified Communications Web API (UCWA) clients, you receive the following error message:
We can’t sign you in because you aren’t set up to use Skype for Business. Please contact your support team
After you apply this update, you receive the following error message:
Your account does not allow access from outside your organization’s network. Please contact your organization’s network and then try signing in
To fix this issue, install the December 2017 cumulative update 6.0.9319.510 for Skype for Business Server 2015, Web Components Server.