Of all the times for Xbox Live to be experiencing "limited service".
Microsoft's Xbox Live has been having some pretty serious issues for the past hour or so.
I could sign into my account (both in a browser and on my Xbox One), but couldn't sign into Titanfall or access stores. Your mileage may vary; others can access the stores, but are having trouble signing in in the first place.
Right now Microsoft's Xbox Live service page is saying that "core services" are "limited".