Symptoms
When you try to specify the maximum number of contacts by using the Set-CsClientPolicy-MaximumNumberOfContacts cmdlet for Microsoft Skype for Business 2015 (Lync 2013), the cmdlet may not work.
Resolution
To fix this issue, install the December 5, 2017, update (KB4011284) for Skype for Business 2015 (Lync 2013).
Note Lync 2013 was upgraded to Skype for Business in April 2015.