When I attempt to look at the keystone leaderboard for my server (link), it displays a message stating “Mythic Keystone Dungeon Leaderboards are only available during an active season. The next season will start soon!”.
Since it is a connected realm, I’ve tried both Whisperwind and Dentarg, but show the same error. Other realms that I have toons on, like Area 52, do seem to load.