You need to troubleshoot issues that Test.User1 reports.
What should you do?
A . Run the Microsoft Support and Recovery Assistant for Office 365.
B . Repair the Office ProPlus installation.
C . Run the hybrid environment free/busy troubleshooter.
D . Run The Microsoft Office Configuration Analyzer Tool.
Answer: C
Explanation: https://support.microsoft.com/en-gb/help/10092/troubleshooting-free-busy-issues-in-exchange-hybrid-environment