Halo: The Master Chief Collection owners are struggling to connect to the game's online matchmaking servers.
Eurogamer has this morning repeatedly tried and failed to get into a game - the loading screen states that no matches can currently be found.
Microsoft has issued a service alert via its Xbox Live Status page and advised that it is now 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."
Launch issues aside, Eurogamer looked fondly at the Halo Master Chief Collection in yesterday's review.
"The Collection is an instantaneous embrace of past and present that combines gaming's powerful sense of nostalgia with its perpetual arms race of processing and graphical power," Nathan Ditum wrote. "It is part of a growing appreciation of the past in a medium which until recently was resolutely forward-looking."