This is how to get the SimConnect protocol to work with opentrack
Go to D:\Microsoft Flight Simulator X - Steam Edition\SDK\Core Utilities Kit\SimConnect SDK\LegacyInterfaces\FSX-XPACK or similarly where you have FSX Steam installed.
Run the SimConnect.msi installer. If you don't have file extensions selected, detail view says Windows installer Package for this file. It has an installer icon. Finish the setup.