Making mission singleplayer and coop and back again?

[Gunfreak]

So I have been working on a mission, decided to do it as a coop mission, most of the mission was done, and I added two F51s, and made them coop playable, and turned the mission from singlepalyer to cooprative. and it worked fine, played it with a friend today. 

But I wanted to fly it as a singleplayer mission too, so I saved it with a singeplayer tag, changed it from cooprativet to single, and deleted both F-51 and made 1 new ones, 1 player and 1 AI. saved it, and added the mission file, to the missions folder, but it won't show up in missions in game

[Space-the-Ace]

Did you check to make sure the Single Player mission was loaded into the missions folder and not the multiplayer folder?  I had made that mistake earlier, missions weren't popping up because they were in the the wrong folder.