ANSWERED: Why am I getting the error "Unable to cast token to token" and what does this mean?

I am adapting the following Roblox script to create a sprint code

local UserInputService = game:GetService("UserInputService")
 
-- Shift keys
local shiftKeyL = Enum.KeyCode.LeftShift
local shiftKeyR = Enum.KeyCode.RightShift
 
-- Return whether left or right shift keys are down
local function IsShiftKeyDown()
	return UserInputService:IsKeyDown(shiftKeyL) or UserInputService:IsKeyDown(shiftKeyR)
end
 
-- Handle user input began differently depending on whether a shift key is pressed
local function Input(input, gameProcessedEvent)
	if not IsShiftKeyDown() then
		-- Normal input
	else
		-- Shift input
	end
end
 
UserInputService.InputBegan:Connect(Input)

Above is the original code.

Below is the code I have at this moment.

local UserInputService = game:GetService("UserInputService")
 
-- Shift keys
local shiftKeyL = Enum.KeyCode.LeftShift
local shiftKeyR = Enum.KeyCode.RightShift
 
-- Return whether left or right shift keys are down
local function IsShiftKeyDown()
	return UserInputService:IsKeyDown(shiftKeyL) or UserInputService:IsKeyDown(shiftKeyR) or UserInputService:IsGamepadButtonDown(Enum.KeyCode.ButtonL1)
end
 
-- Handle user input began differently depending on whether a shift key is pressed
local function Input(input, gameProcessedEvent)
	if not IsShiftKeyDown() then
		game.Players.LocalPlayer.Character.Humanoid.WalkSpeed = 16 -- Normal input
	else
		game.Players.LocalPlayer.Character.Humanoid.WalkSpeed = 32 -- Shift input
	end
end
 
UserInputService.InputBegan:Connect(Input)

And I am getting the following Output:

  18:22:53.803 - Unable to cast token to token
18:22:53.805 - Stack Begin
18:22:53.805 - Script 'Workspace.IncredibleTeamAidan.Run New', Line 9 - function IsShiftKeyDown
18:22:53.806 - Script 'Workspace.IncredibleTeamAidan.Run New', Line 14 - function Input
18:22:53.807 - Stack End

It appears that the issue is with detecting the buttons pressed in lines 8 to 10

local function IsShiftKeyDown()
	     return UserInputService:IsKeyDown(shiftKeyL) or UserInputService:IsKeyDown(shiftKeyR) or UserInputService:IsGamepadButtonDown(Enum.KeyCode.ButtonL1)
end

however I believe it could be with line 21

 UserInputService.InputBegan:Connect(Input)

If anybody knows how I may be able to adjust this to work, that would be much appreciated

Other Information: Code is within a local script, stored in Game.StarterPlayer.StarterCharacterScripts