Edit: Misplacedyank is in the comments letting us know that it's actually an issue with Microsoft's Azure services. It appears that this goes all the way up, I'm sure it's a priority fix and outside of 343's control.
I personally was playing Infinite fine until about 15 minutes ago and have received 'Dedicated server error' messages when trying to find a game since then.
It's not just you, or me.
Hoping they go back up soon, BTB Fiesta is one of my favourite game modes and I'm sure many people are excited about the Reach modding tools for customs etc. Terrible time for servers to go down.
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