SimFX window not loading on Xbox, module wasn't able to initialize.
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On your Xbox Series X|S console, launch My games & apps. Navigate to Games, and place the cursor over Microsoft Flight Simulator. Press the menu button (three lines) on the controller, and select Manage game and add-ons from the context menu. Within the context menu, press the menu button on the Microsoft Flight Simulator tile and select “Manage installation …” Navigate to the Downloadable add-ons area and press X on “Microsoft Flight Simulator Add-on Support” Uninstall / Delete "Add-on Support". Then restart the Console and launch the sim, it should reinstall that component.
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