After installing SysManSMS Server on Windows Server 2012 you may encounter a message saying that “Microsoft .NET Framework 3.5 cannot be installed…” when setting up the tray menu tool.
Windows Server 2012 requires you to install .NET Framework 3.5 using the Server Manager GUI, or the DISM (Deployment Image Servicing and Management) command. The latter is the simplest solution. Open a command prompt with elevated rights (right-click and select “Run as Administrator”), and run the following command:
dism /online /enable-feature /featurename:NetFX3 /all /Source:d:\sources\sxs /LimitAccess
This will install the .NET Framework version 3.5 on your Windows Server.
Note that the SysManSMS Service itself does not require .NET Framework and you can run SysManSMS without installing .NET Framework 3.5.