I did not consciously make any changes to GSX.
deleting the configuration file in the appdata/roaming/virtuali/NGX (forget the exact extension of the NGX folder)
If you HAD a configuration file for the NGX in the %APPDATA%\virtuali\Airplanes folder (this is the correct folder), it means you HAVE configured the airplane using the editor, or you downloaded a file shared here. On a fresh GSX install, no .INI files for airplanes are installed.
Both are not needed for the NGX, since it's natively supported so, you must simply be sure that no .INI files for the NGX are present in the %APPDATA%\virtuali\Airplanes folder, and if you have multiple folders, you must remove them all, for each NGX variant.
And, you will probably have to re-select your airplane again OR use the "Restart Couatl" option in the Couatl main menu, otherwise the changes won't be applied.