Why isnt this working?

On line 6, you try to access Spawns as a table, but it is just referring to a Model in the Workspace. SpawnsGet is a table. Also, you run the in pairs loop after the script already chose the random spawn. Instead, your script needs to choose a different random spawn each time.

Another thing I changed; I made it so it gets a fresh list of the SpawnLocations each time a player spawns, because I am assuming this game will have multiple maps, and therefore have different sets of spawns. If you don't like this modification, just remove line 13 and change line 8 to: local Spawns = Map:WaitForChild('Spawns'):GetChildren()

--local Player = game.Players.LocalPlayer
-- ^ Remove that, because this is Server code, and should 
-- therefore go inside a "Script" (not "LocalScript")

-- Paste this code in a "Script" inside ServerScriptService

local Map					= game.Workspace:WaitForChild('Map')
local SpawnLocations		= Map:WaitForChild('Spawns')

game.Workspace.ChildAdded:connect(function(plr)
	if plr:IsA('Model') and plr:FindFirstChild('Humanoid') then -- Do you have things spawning in your Workspace that are not a Model, but have a Humanoid?
		local Spawns = SpawnLocations:GetChildren() -- Get an up-to-date list of the Spawns
		Player.Character:MoveTo(Spawns[math.random(#Spawns)].Position) -- Choose a random Spawn and teleport Player to it
	end
end)