Attempt to index nil with 'FindFirstChild'?

As the title says, 'FindFirstChild' is a nil value. It's on the second line of code. Can someone help me?

for keyvalue, player in pairs(game.Players:GetPlayers()) do
			if player.Character:FindFirstChild("Humanoid") then
				if player.Character.Humanoid.Health >= 1 then
					table.insert(PlayersInGame, keyvalue, player)
					player.Team = game.Teams.Players
					player.Character.Humanoid.Died:Connect(function()
						for i = 1, #PlayersInGame do
							if PlayersInGame[i] == player then
								SelectBox(player.Character:FindFirstChild("PlateValue").Value)
								local TransInfo = TweenInfo.new(
									2,
									Enum.EasingStyle.Linear,
									Enum.EasingDirection.Out,
									0,
									false,
									0
								)
								local Tween = TweenService:Create(player.Character:FindFirstChild("PlateValue").Value, TransInfo, {Transparency = 1}):Play()
								coroutine.wrap(function()
									wait(2)
									player.Character:FindFirstChild("PlateValue").Value:Destroy()
								end)
								table.remove(PlayersInGame, i)
								if player.Team == game.Teams.Players then
									player.Team = game.Teams["Lobby"]
								end
							end
						end
					end)