FH4 rendered unplayable

First I lost progress due to sync error after I reinstalled the game. Then the stupid save mysteriously came back and worked fine for two days. Now I can’t go beyond the main menu because, apparently, my “profile is invalid”. Error code E47-0. Why is this game in such a state? There is no offline mode, the saves vanish on their own, the slightest network lag is an excuse screw up, and lastly, the multiplayer is dead.
I want a fix for this invalid-profile problem without having to download the game again(because I can’t).