Players who can't connect to the Gotham Knights aren't to blame, as WB Games Montreal has taken down the Gotham Knights servers this January 24 for maintenance!
The server in the game is in a pretty long period of maintenance during which co-op will be unavailable. Here's the news from the developers:
Here's how to change your timezone.
As you can see, the game's servers will be down for seven hours, so players will be unable to connect for seven hours. If there's a patch released during or after the maintenance, as is often the case for games, we'll make sure to inform our readers.
If there is a new patch for Gotham Knights, bookmark the game hub.