It looks like hackers have made the online mode inaccessible to xbox and pc players
The Killer Instinct Ranked mode was hacked and is now unavailable for playing for Windows and Xbox users. Nicolas "Nicky" Iovene was the first to report this on his personal Twitter account, noting that other multiplayer features such as Exhibition, Lobbies, and Records still work correctly.
Another Killer Instinct core community member, Eric "N1ghtslash" De Jesus, also noticed the problem, laying out several screenshots demonstrating an error when entering this mode.
Previously, Killer Instinct was subjected to hacking attempts, which primarily affected the rating ladder of players, where the attackers entered information about profiles that had not previously participated in online competitions. These actions likely affected the inoperability of the ranking mode in which this ladder was formed.
At the time of this writing, the Rare team does not have a notification about the existing problem and the timing of its elimination. We hope that Killer Instinct will not be left without such a primary mode for competitions and training for a long time.
Update: The developers are aware of the problem and are already working on fixing it: