Owners of Halo: The Master Chief Collection are reporting issues connecting to the game's online matchmaking servers, according to posts made on Reddit and Halo Waypoint.
Users are currently having to wait hours to connect, with some finding only a few available matches within a six hour period.
Microsoft has since issued a service alert over its Xbox Live status page, confirming it is investigating the problem.
"Xbox members, are you having a tough time matchmaking in Halo: The Master Chief Collection?" Microsoft wrote. "As you read this message, we're working with our external partner to correct this issue right away.
"We appreciate your patience in the meantime! We'll update you again when we have more information."
As was previously reported, the game appears to be experiencing some additional issues to some of its multiplayer playlists. As a result, Halo: Combat Evolved-specific playlists are not available at launch, while other changes to the existing playlists will exclude some games and maps.