In Skype for Business Server 2015 and Skype for Business Online, the LastActive attribute occasionally shows outdated information (for example, a user may see a colleague who was online yesterday as "Offline 88 days"). This behavior may occur even when the LastActive attribute is disabled.
A user whose LastActive attribute is incorrect can resolve the inaccurate time stamp by signing out and in or by manually changing their presence.
Article ID: 3056287 - Last Review: Apr 19, 2017 - Revision: 15
Skype for Business Online