Assume that you implement a new setting which is named as CustomSafeUrlPrefixes in Microsoft Skype for Business 2015 (Lync 2013). URLs that begin with one of your custom URL prefixes will correctly show as clickable links within chat messages. But if you click these links, the expected URL won't be launched in a browser.
To fix this issue, install the January 3, 2017, update (KB3141468) for Skype for Business.
Note Lync 2013 was upgraded to Skype for Business in April 2015.