Just like Outlook, Lync has a bad habit of accumulating junk. When an end user is experiencing strange, unpredictable problems with Lync, one of the first things I do after confirming they have the correct configuration settings, is to delete these folders and registry settings:

For Lync 2010

Delete these folders:

• %appdata%\Microsoft\Communicator
• %localappdata%\Microsoft\Communicator

Delete these registry keys:

• Any keys under HKCU\Software\Microsoft\Communicator\ that are named with either a computer name or a user name.

For Lync 2013+ and Skype for Business

Delete these folders, but change the version number to match your installed version of Office:

• %appdata%\Microsoft\Office\15.0\Lync
• %localappdata%\Microsoft\Office\16.0\Lync

Delete these registry keys:

• Any keys under HKCU\Software\Microsoft\Office\16.0\Lync\ that are named with either a computer name or a user name.

Note that, even though you have Skype instead of Lync, the data paths still say “Lync”.

These steps won’t solve every problem, but–just like rebooting Windows–they will solve most of them.

P.S. Do you know what this little symbol in the bottom left corner of a Lync contact’s status indicator means?

Lync Out-of-Office indicator

That’s the Out of Office indicator. If your contact has their out of office status turned on in Microsoft Outlook, their Lync presence indicator will include this little Union Jack looking thing at the bottom.