The remote event wont fire and i have no idea how to fix this?

Client

local plr = game.Players.LocalPlayer
local char = plr.Character
local UIS = game:GetService("UserInputService")
local Mouse = plr:GetMouse()
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local RP = game:GetService("ReplicatedStorage")
local Remote = RP.FireBallRemote
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local Debounce = true
local Key = "Z"
local ButtonDown = false

UIS.InputBegan:Connect(function(Input, IsTyping)
    if IsTyping then return end
    local KeyPressed = Input.KeyCode if KeyPressed == Enum.KeyCode[Key] and Debounce and char then
        Debounce = false
        ButtonDown = true
        Remote:FireServer(ButtonDown, Mouse.Hit,UIS)
        print("fired")
    end 
end)

Server

local UIS = game:GetService("UserInputService")
Remote.OnServerEvent:Connect(function(Player,Down,HitPosition)
    -- code here
end)