Why did my campaign pass expire?

I bought a Gun Mettle campaign pass a while ago, and, as far as I know, it's supposed to last until September 30th. Mine appears to have disappeared though; did I complete all the contracts I can so it expired?

The Team Fortress 2 item servers are likely down or under maintenance - the game has no idea whether you have the Gunmettle Campaign coin, meaning it's trapped in your backpack with the rest of your items. (If you've bought the ticket but haven't activated it, it will also be trapped).

You'd be best to wait for the item servers to come back up and try again later.

You can use status.tf2lists to check the status of item servers