Some players flocking to Halo 4's multiplayer on its release day are having a tough time getting online. Users are reporting issues with server availability both for competitive matches and Spartan Ops, and 343 Industries has acknowledged it's working on the problem.
Affected players receive "Server Unavailable" messages errors and may be unable to participate in the game's online modes. Some matches do work, but players have reported XP not being properly rewarded upon their conclusion, and that they have had difficulties with joining friends or adjusting equipment.
While the issue isn't afflicting all players, 18 pages of response on the official Halo Waypoint forum thread indicates it may be fairly widespread.
"As you can imagine, there are a tremendous number of new players connecting to Halo 4 right now," an administrator said on the thread. "We’re aware that some users are experiencing occasional issues connecting to the Halo 4 services. Please bear with us as we continue to work through these issues during the launch period."