We have now deployed a fix and the event should be visible again for all players. If it is not showing up in your game, please restart the app.
It may take a few minutes before rankings display on the leaderboard, but no progression should have been lost. We will continue to monitor the situation.
We apologize for any inconvenience caused. Thank you for your patience and understanding.
Initial Post (2022-01-05, 08:55 UTC):
There is currently a known issue with the Clash of Knights Alliance Quest and we have had to disable it. We are investigating the issue and trying to get it resolved as soon as possible. Our apologies for the inconvenience.
We will post any updates to this issue here.