Walkspeed gamepass not giving the player extra speed?

This walkspeed gamepass is not giving the player extra speed if owned. Here's my script:

local passId = 4650300 
game.Players.PlayerAdded:connect(function(player)
    local function isAuthenticated(player)
       return game:GetService("GamePassService"):PlayerHasPass(player, passId)
    end
	print("i think it works")
    if isAuthenticated(player) then
  		repeat wait() until player.Character.Humanoid
        player.Character.Humanoid.WalkSpeed = 24---Change this line to what you want the Game Pass to do.
		print("it does work!")
    end
end)

It prints "i think it works" but it doesn't print ("it does work")

Also, as an extra, how could I make it so that the player can buy the gamepass in game? Thanks.

local passId = 4650300
local function isAuthenticated(player)
	return game:GetService("GamePassService"):PlayerHasPass(player, passId)
end

game.Players.PlayerAdded:connect(function(plr)
	if isAuthenticated(plr) then
		repeat wait() until game.Players.LocalPlayer.Character.Humanoid
		game.Players.LocalPlayer.Character.Humanoid.WalkSpeed = 24
	end
end)

You should not have functions inside of the PlayerAdded event. Hopefully this works, I didn't try it though.