Projectile attack fully works in studio test mode, however not in play mode?

(My filtering enabled is off)

local tool = script.Parent
local player = tool.Parent.Parent
local mouse = player:GetMouse()
local root = player.Character.HumanoidRootPart


tool.RemoteEvent.OnServerEvent:connect(function(player,mousehit)
	if player.Character:FindFirstChild("multiattackprevention") then return end
	local multiattackprevention = Instance.new("StringValue")
	multiattackprevention.Parent = player.Character
	multiattackprevention.Name = ("multiattackprevention")
	local hitcooldown = false
	local animation = player.Character.Humanoid:LoadAnimation(tool.SuperJump)
	animation:Play()
	local bv = Instance.new("BodyVelocity")
	bv.Parent = player.Character.Torso
	bv.Velocity = Vector3.new(0,250,0)
	wait(1)
	bv.Velocity = Vector3.new(0,0,0)
	wait(0.01)
	bv:Destroy()
	wait(0.4)
	player.Character.Torso.Anchored = true
	root.CFrame = mouse.Origin
	local animation2 = player.Character.Humanoid:LoadAnimation(tool.Cast)
	animation2:Play()
	wait(0.5)
	local magmadrag = Instance.new("Part")
	magmadrag.Transparency = 0.5
	magmadrag.Parent = game.Workspace
	magmadrag.Position = player.Character:FindFirstChild("Right Arm").Position
	magmadrag.CanCollide = false
	magmadrag.TopSurface = ("Smooth")
	magmadrag.BottomSurface = ("Smooth")
	magmadrag.BrickColor = BrickColor.new("Bright red")
	magmadrag.Material = ("Ice")
	magmadrag.Size = Vector3.new(30,30,30)
	local bv = Instance.new("BodyVelocity")
	bv.Parent = magmadrag	
	bv.MaxForce = Vector3.new(1e8,1e8,1e8)	
	bv.Velocity = mouse.Origin.lookVector * 150
	local sound = Instance.new("Sound")
	wait(0.5)
	magmadrag.CanCollide = true
	multiattackprevention:Destroy()
	wait(0.5)
	player.Character.Torso.Anchored = false
	magmadrag.Touched:connect(function(hit)
		magmadrag.Anchored = true
		bv.Velocity = mousehit.lookVector * 0
		if hitcooldown == true then return end
		local enemy = hit.Parent:FindFirstChild("Humanoid")
		if enemy == player.Character.Humanoid then return end
		if enemy then
			enemy.Health = enemy.Health - 400
			hitcooldown = true
			wait(3)
			magmadrag:Destroy()
		else wait(3)
			magmadrag:Destroy()
			wait(0.5)
		end
	end)	
	wait(10)
	magmadrag:Destroy()
end)	

So this script runs perfectly fine in studio test mode, however in play mode, the player jumps up but then simply stays anchored in the air and doesn't fire the projectile.

In play mode server log I get the error:

Players.Citranix.Backpack.Magma Dragon.Script:24: attempt to index upvalue 'mouse' (a nil value)

I do not want the projectile to fire towards the original mouse hit which fired this function, I want it to delay and then shoot towards where the players mouse currently is.