The other resolution to this issue involves updating the ProxyAddresses Active Directory attribute to include the SharePoint user’s Lync address. This is especially important if the Lync and SharePoint environments aren’t in the same domain or forest. For example, if SharePoint is hosted on-premises but users sign in to Skype for Business Online (formerly Lync Online) through Office 365, you should update the ProxyAddresses Active Directory attribute in this manner. As long as the ActiveDirectory object that's associated with the SharePoint user contains the user’s Lync sign-in address in the ProxyAddresses attribute, presence should display for that contact.
If you have Exchange tools available, populate the ProxyAddresses attribute by using the method that's described in the following Microsoft Knowledge Base article:
This article applies primarily to Skype for Business Online and SharePoint Server on-premises integration. However, it can also be used for an installation of Lync Server that has SharePoint Online integration as long as directory synchronization is enabled.
Article ID: 2813701 - Last Review: Dec 28, 2016 - Revision: 1