Why does UserinputService not work for left shift in my local script?

I have a local script that uses UserInputService in StarterPlayerScripts and it works with the "J" and "K" keys, but does not work for the "LeftShift" key. This is my local script:

--Variables
local Player=game:GetService("Players").LocalPlayer
local Character=Player.Character or Player.CharacterAdded:Wait()
local Humanoid=Character:WaitForChild("Humanoid")
local UIS=game:GetService("UserInputService")

--Key(s) Down
UIS..InputBegan:Connect(function(Key,gameProcessedEvent)

--J
if Key.KeyCode==Enum.KeyCode.J then
print("J was pressed!")
end

--K
if Key.KeyCode==Enum.KeyCode.K then
print("K was pressed!")
end

--Left shift
if Key.KeyCode==Enum.KeyCode.LeftShift then
print("Left shift was pressed!")
end
end)

--Key(s) Up
UIS.InputEnded:Connect(function(Key,gameProcessedEvent)

--Left Shift
if Key.KeyCode==Enum.KeyCode.LeftShift then
print("Left shift was released!")
end
end)

J and K are working, left shift is not working. I know that it is not "UIS.InputEnded" that is breaking it because "UIS.InputBegan" isn't even working for left shift. I am not going to use any other method for keydown events, so please do not put that in any of your answer(s). Thank you to any answer(s) in advanced.

You don't have to write two different Statements to reenact as if you were holding down a key, UserInputService has an Event that covers this up for us, simply use

UserInputService.InputBegan:Connect(function(UserInput, IsTyping)
   if (UserInput:IsKeyDown(Enum.KeyCode.LeftShift) and not isTyping) then
      print(game.Players.LocalPlayer.Name.." is holding the '"..UserInput.."' key!")
   end
end)

Although you said you weren't going to use other methods, I do suggest taking a look at this.

For ContextActionService, this is what it should look like, I'm not too much of a wiz on this Service but I know enough to show an example, I most likely wont be able to provide a proper explanation, so please see https://developer.roblox.com/api-reference/class/ContextActionService for more information!

local ContextActionService = game:GetService("ContextActionService")
local Player = game:GetService("Players").LocalPlayer
local function ResetCharacter()
   local Character = Player.Character or Player.CharacterAdded:wait()
   local Head = Character:FindFirstChild("Head")
   if (Head) then
      Head:Remove(); wait(1); Player:LoadCharacter()
   end
end
ContextActionService:BindAction("ResetButton", ResetAvatar, true, "R")
ContextActionService:SetPosition("ResetButton", UDim2.new(Vector2, Vector2))
ContextActionService:SetImage("ResetButton", "bxassetid")

Most Users prefer or recommend this Service over UserInputService, yet honestly, for my personal opinion, I wouldn't, I find it too confusing, I'll try to explain what's going on:

Most see above can be recognized as Indexing, and writing functions. That's exactly what it is no more. Except when it comes to :BindAction(), this is the first step, this BuiltInFunction has four arguments: (Reference name; variable, function; event that occurs when tapped, if the button should be functional or not; boolean, same event occur when "key" is pressed on computer). This ultimately sets up the Button, for those who don't understand what I mean by Button, ContextActionService is a Service built to make mobile devices compatible with computers. This Service creates a button similar to the Jump button seen on mobile devices.

After this we have optional advancements, such as customary positioning, yet remember, the first argument always consists of the reference name. Then theres setting a customary Image for the Button, reading the arguments displayed should be pretty self explanatory.

After this, let the Script run, make sure to test this whilst in Emulation mode.

Hope this helps you out, if so, don't forget to Upvote and Accept this Answer!