FortiClient EMS Microsoft Visual C++ installation
The EMS installation includes installation of Microsoft Visual C++ (VC) 2015. If the server already has a newer version of VC installed, the installation fails. See VC++ 2015 Redistributable installation returns error 1638 when newer version already installed.
If you have a version of VC installed on your server that is newer than 2015, uninstall VC before installing EMS.
SQL Server Enterprise with 5000 or more endpoints
When managing more than 5000 endpoints, install SQL Server Enterprise instead of SQL Server Express, which is installed with EMS by default. Otherwise, you may experience database deadlocks. See the FortiClient EMS Administration Guide.