On September 20, a change is coming to how crates will be opened in H1Z1: Just Survive. In preparation for this change, we wanted to let you know about this update.
NO KEYS, JUST CRATES
As of September 20, crate keys will be removed from the game. Since keys are being removed from the game, all keys currently in player inventories will be converted to standard unlocked Predator crates. If you would like to use your key to open a different crate, you will need to do that before the game update on September 20.
You will still need to use Daybreak Cash to open locked crates, and you can also use Daybreak Cash to purchase unlocked crates, after keys are removed.
Source: Daybreak Website