Skype for Business – Cannot sign in because the server is temporarily unavailable

An issue was reported to me recently where a user was unable to login to Skype for Business / Lync.

The steps attempted to diagnose this issue were as detailed below.

  • Attempted to login with my Skype for Business user account (fail)
  • Run Skype for Business as my user (success)
  • Run Skype for Business as Administrator (success)
  • Try another computer as that user (fail)

The user was logged into a computer on a domain where AD FS is configured for Office 365 and attempting to authenticate against a different organisations Skype for Business tennant.

After endless troubleshooting, I discovered a blog post with someone having the same issue and documenting a fix.

In my situation, as the user was using Microsoft Office 2016, the resolution was to open regedit and create the following entry.

HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\16.0\Lync

Name: DisableNTCredentials  Type: REGDWORD Value:1

I hope this helps someone somewhere!