Ok. A year ago I had the same issue after I refreshed my Surface. When you do that, it requires you to rename your device. I used the exact same name it already was using. Took me a while to figure this out, but there is some compatibility issue if it sees two devices identified identically. I couldn't sync my Microsoft app, I couldn't log into Xbox live, etc. I deleted the profile for the name of the device it was originally called and it fixed it all.
That being said, I just had the sync issue appear again. This time it happened at the exact same time my twitter account vanished. I couldn't get in it. Couldn't reset it. Contacted twitter and they say there is no account I'm mentioning and there never has (even though it is a four year old account). So I'm sitting in the same boat as you. My email app keeps saying I have a security certificate issue. Trying to resync apps on Windows 8 fails out. Ugh, ugh, ugh.