In Metal Gear Solid 5: The Phantom Pain, I know the ending mission is 46. How do you unlock the mission so you can play it and watch the ending?

Edit 1: 

I got that ending but it still will not unlock for me. I got the cassette tape at the end and all.

Edit 2: 

Here are the screenshots (MAJOR SPOILERS): steamcommunity.com/sharedfiles/filedetails/?id=519951201 and steamcommunity.com/sharedfiles/filedetails/?id=519951450 (Spoiler tags enabled for each)