Load Modified Mission Error 10020

[vonPilsner]

So I modified a mission and put the mission files in a subfolder of the 'Missions' folder and I can see the mission in-game and load it, but when I press start I get: Error 10020 This mission is unavailable for your account.

 

Any way to load a customized mission in game? (I really hope so) 

[vonPilsner]

Same result when I take a game-generated mission and move it into a 'Missions' subfolder.