When trying to create a new Skype meeting from Outlook we get the message “The request failed. Please try again. Make sure that you are signed in to Skype for Business.”

First solution was to clear outlook name cache. This solves the problem for a short while.

A better workaround is to disable outlook the use of UCAddin.dll.[HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\16.0\Lync\AddinPreference]
“RecipientResolutionMode”=dword:00000002

Then close and restart Lync/S4B. This is a “bug” in a windows update to the Skype client.