If Expedition is curently ongoing but is unavailable to you, there are several reasons why it can happen:

• The event opens after level 26 and after you've finished renovating Austin's room. Make sure you have achieved these milestones in the game.

• If you're certain the above conditions are met, the issue may lie in your device performance characteristics. Expedition cannot be launched on some older Android and iOS models - even if the game itself can be installed and is running without interruptions. In this case, you can try playing on a different, more powerful device.

• If none of the above applies to you, please check this article that lists other common reasons why events don't appear:
  An event doesn't start or disappeared: homescapes://helpshift/185/16637