Load Mission Button

Im looking to create a load mission button, to put on my MainMenugui, that will simply load up my mission. I have tried the method used in the tutorial.base example, and it worked for me previously but for some reason it no longer works. I cant see what I could have changed to make it so, but Ive been unable to get it working again. Ive browsed the forums, and found a few functions that people said would work, but I put them into the main.cs and no luck. So can anyone help just to give me a function that'll allow me to have a button to load my mission on the mainmenu page? Thanks