Did you assign your ground the Lava tag? Did the collision actually trigger?
Do the involved objects have colliders and rigidbodies?
Also please use code tags to post code
Edit: Also, what is this script attached to? I see you are using a Transform player, so i assume the Death object itself is not attached to the player? But if so, the Death object colliding with Lava does not make a whole lot of sense. If Death is attached to the player you can just use its own transform, since that would be the players’.