Attempt to connect failed: Passed value is not a function?

I was going to make a Spectate Function so you can see other players camera

I keep getting a error saying that it attempted to connect but failed because Passed Value is not a function. Thats not right because i already setup the functions.

Heres my code and the exception happend at line 25 and 26 Which is script.Parent.Parent.Style.Forward.MouseButton1Click:connect(GoForward) script.Parent.Parent.Style.Back.MouseButton1Click:connect(GoBack)

script.Parent.MouseEnter:connect(function()
    script.Parent:TweenPosition(UDim2.new(0,0,0.3,0),"Out","Quad",0.1)
    script.Parent.Parent.Parent.MouseOver:Play()
end)

script.Parent.MouseLeave:connect(function()
    script.Parent:TweenPosition(UDim2.new(0,-20,0.3,0),"Out","Quad",0.1)
end)

players = {}

PChoice = 1

script.Parent.MouseButton1Click:connect(function()
    Spectating = false
    script.Parent.Parent.Parent.MouseClick:Play()
    if script.Parent.Selected == false then
        script.Parent.Selected = true
        script.Parent.Parent.Style.Visible = true
        for i,v in ipairs(Game.Players:GetChildren()) do
            if v.Name ~= game.Players.LocalPlayer.Name then
                table.insert(players,v)
            end
        end
        script.Parent.Parent.Style.Forward.MouseButton1Click:connect(GoForward)
        script.Parent.Parent.Style.Back.MouseButton1Click:connect(GoBack)
    else
        script.Parent.Selected = false
        script.Parent.Parent.Style.Visible = false
        game.Workspace.CurrentCamera.CameraSubject = game.Players.LocalPlayer.Character.Humanoid
    end
end)

while true do
    if game.Players.NumPlayers == 1 then
        script.Parent:TweenPosition(UDim2.new(0,-150,0.3, 0),"In","Quad",0.5)
    else
        script.Parent:TweenPosition(UDim2.new(0,-15,0.3, 0),"Out","Quad",0.5)
    end
    wait()
end

function GoForward()
    PChoice = PChoice + 1
    if PChoice >= #players then
        PChoice = 1
    end
    game.Workspace.CurrentCamera.CameraSubject = players[PChoice].Character.Humanoid
end

function GoBack()
    PChoice = PChoice - 1
    if PChoice <= 1 then
        PChoice = #players
    end
    game.Workspace.CurrentCamera.CameraSubject = players[PChoice].Character.Humanoid
end

Heres the error i got

10:28:27.170 - Attempt to connect failed: Passed value is not a function 10:28:27.170 - Script 'Players.Player2.PlayerGui.Spectate.Button.System', Line 25 10:28:27.170 - Stack End 10:28:27.170 - Attempt to connect failed: Passed value is not a function 10:28:27.170 - Script 'Players.Player2.PlayerGui.Spectate.Button.System', Line 26 10:28:27.170 - Stack End