Xbox One matchmaking is not working as intended at the moment, Microsoft has announced.
According to the latest update from the Xbox Live Status page, the issue affects Xbox One players trying to join others in online games.
It's unfortunate timing, actually, as 343 Industries just released a patch for Halo: The Master Chief Collection designed to fix that game's matchmaking. Frustrated gamers are unlikely to realise there's a broader matchmaking issue.
Multiple games have been affected by the problem, judging by Twitter chatter. The Xbox 360 does not seem to be affected.
For once, it seems like nobody has claimed responsibility for the outage.