Technician report is not working after upgrading to 10.8+

If when you try to open Reports - Technician Report, you see this:

Please check the server's log - launch "eventvwr.exe," and choose the "Application" log - for errors or warnings from the helpdesk app. If you see an error like this:

System.Data.SqlClient.SqlException (0x80131904):
The PERCENTILE_CONT function is not allowed
in the current compatibility mode.
It is only allowed in 110 mode or higher.

You will need to run the following query on your SQL Server:

ALTER DATABASE JitbitHelpDesk
SET COMPATIBILITY_LEVEL = 110

After that the report should work.