Not too long ago there were reports circling that an issue was found throughout Metal Gear Solid V: The Phantom Pain. According to reports, this problem didn’t allow for players to progress or save in Mission 29 or Mission 42.
This problem has been recently fixed with the lastet update that was pushed out on Steam. A bug was also fixed within this latest update that stopped players from progressing throughout the tutorial. This update was automatically downloaded for anyone that is playing MGSV on Steam.