Which plugin am I missing to run 3CX Phone for Windows properly with the Busylight?

You need to edit the file named "3CXWin8Phone.user.config", adding the name of your DLL to the following entry

Located at: C:\ProgramData\3CXPhone for Windows\PhoneApp\3CXWin8Phone.user.config

This line needs to be present for our software to be loaded:

<add key="CRMPlugin" value="CallTriggerCmdPlugin,DotNetScriptPlugin,BusylightPlugin" />

The 3CXPhone logs located at "%AppData%\3CXPhone for Windows\Logs" will tell you what addins are being loaded.

Please note that this requires that 3CX has a PRO/Enterprice license key activated, otherwise your plugin will be ignored.