Effect fades away when they buyer of my Game Pass died? [SOLVED]

This is a problem which my game pass effects wont last long when the buyer died. They will get the effect when they bought the pass, but it will fade away instantly when they died

game.Players.PlayerAdded:connect(function(plr)
    if isAuthenticated(plr) then
        local name = plr.Name
        if name then
            local check = game.Workspace:FindFirstChild(name)
            if check then
                checkHumanoid = check:FindFirstChild("Humanoid")
                if checkHumanoid then
                    checkHumanoid.WalkSpeed = 16 * 2
                end
            end
        end
    end
end)

-- this do not work...
while checkHumanoid.WalkSpeed ~= 16 *2 do
    checkHumanoid.WalkSpeed = 16 *2
end

i already the Died event, still, it wont work, any answers?