Error Code 0x15 of Microsoft Office commonly occurs because of an existing installation of MS Office pack in your computer system. Please note that this error is relevant to all the editions of Microsoft Office 2013, office 2016 and Microsoft Office 365.

Office 365 Error Code 0x15 Solutions:
This can occur in the below enlisted versions of the MS Operating System

Windows Server Edition of the year 2012/2008
Windows 7 /8 /8.1/10
You can also check the event log for more information about office installation errors by selecting the event source VSTO4.0 from windows application logs. Here providing some examples screenshots of how to check log and office licensing event issues.