Why This Script is not killing players when they touch the Random Chosed Map?

You can't check if children were touched using :GetChildren(), the correct way to do this is using a for loop and get the children from there.

local mapStorage = game.ServerStorage.Maps:GetChildren()
local Players = game:GetService("Players")
local chosenMap = mapStorage[math.random(1, #mapStorage)]
chosenMap.Parent = workspace.CurrentPlaying
print("Map chosen is; "..chosenMap.Name.." Map")

local touchMapDie = chosenMap:GetChildren()

for i, v in pairs(touchMapDie) do --Gets the children of the chosenMap
	if v:IsA("Part") then
	v.Touched:Connect(function(hit) --Check if a child was touched
		if Players:GetPlayerFromCharacter(hit.Parent) then --Check if the part touching is a player
			hit.Parent.Humanoid.Health = 0 --Kills the player
		end
	end)
	end
end