As @lionel760x mentioned and it seemed to work, replace the parts of code that they mentioned, and now, it doesn’t seem like it’s playing the sound, so then add WalkSound:Play()
local speed = 0.7
local Players = game:GetService("Players")
Players.PlayerAdded:Connect(function(player)
local WalkSound = player.Character:WaitForChild("HumanoidRootPart").Running
WalkSound.SoundId = 133705377
WalkSound.PlaybackSpeed = speed
WalkSound.Volume = 1.5
WalkSound:Play()
end)
game:GetService("ReplicatedStorage").Death.OnServerEvent:Connect(function(player)
local character = game.Workspace:WaitForChild(player.Name)
local WalkSound = character:WaitForChild("HumanoidRootPart"):WaitForChild("Running")
WalkSound.SoundId = 133705377
WalkSound.PlaybackSpeed = speed
WalkSound.Volume = 1.5
WalkSound:Play()
end)