Help with getting players in server?

Your script should be put into serverscriptservice, not serverstorage. You shouldn't be using :WaitForChild() if you are checking to see if an item exists. :WaitForChild() will wait forever until that item exists, even if it will never exist. If you are checking to see if an item exists, then use :FindFirstChild(), if you know an item will eventually exist and hasn't been created/loaded yet, then use :WaitForChild(), otherwise your script will wait forever.

This should fix your problems.

local sword2level = 5
local sword3level = 10
local sword4level = 20
local players = game:GetService'Players' -- If the player service doesn't already exist
print("0")

while wait() do
	repeat wait() until players.NumPlayers >= 1 -- Wait until there is 1 or more players in the game
	for _, player in pairs(players:GetPlayers()) do
		print("1")
		local shop = player:FindFirstChild("Shop")
		if shop then
			print("2")
			 local stats = player:FindFirstChild("leaderstats")
			if stats then
				print("3")
				local level = stats:FindFirstChild("Level")
				if level then
					print("4")
					level.Changed:connect(function(playerLevel)
		                            print("5")
		                            if playerLevel >= sword2level then
		                                print("6")
		                                shop:WaitForChild("KnightsSword").Value = true
		                            elseif playerLevel >= sword3level then
		                                shop:WaitForChild("ShadowDancer").Value = true
		                            elseif playerLevel >= sword4level then
		                                shop:WaitForChild("OrcBlade").Value = true
		                            end
		                        end)
				end
			end
		end
	end
end