Aircraft loads up dead, no activation window, no landing gear (SimConnect issue)

This issue is caused by an incorrect SimConnect runtime installation on your computer, follow these instructions to fix it:
 
  1. Navigate to this folder:

    <FSX:SE root folder>\SDK\Core Utilities Kit\SimConnect SDK\lib

    (By default the <FSX root folder> is C:\Program Files (x86)\Steam\steamapps\common\FSX)
     
  2. Run the SimConnect.msi installer file inside the folder.
     
  3. Navigate to this folder:

    <FSX:SE root folder>\SDK\Core Utilities Kit\SimConnect SDK\LegacyInterfaces

    Inside this folder are three more folders that each contain a SimConnect.msi file - run all three of them.