Forcing Lync 2013 client to download address book

To force Lync Server 2013 to update the address book, execute the following cmdlet:

Update-CsAddressBook

Wait for the LS Address Book Server event to report event ID 21056. Then for the following respective clients do the following:

Lync 2010 Log off of the Lync client and delete the profile from:

%userprofile%\AppData\Local\Microsoft\Communicator

Then execute the following command in the command prompt to add the registry that forces the Lync client to immediately download the address book:

reg add HKLM\Software\Policies\Microsoft\Communicator /v GalDownloadInitialDelay /t REG_DWORD /d 0 /f

Lync 2013
Log off of the Lync client and delete the profile from:

%userprofile%\appdata\Local\Microsoft\Office\15.0\Lync

Then execute the following command in the command prompt to add the registry that forces the Lync client to immediately download the address book:

reg add HKLM\Software\Policies\Microsoft\Office\15.0\Lync /v GalDownloadInitialDelay /t REG_DWORD /d 0 /f

Cheers!