Players.Error_ScreenRP.Backpack.Long.LocalScript:28: attempt to index nil with 'GetMouse' is the issue that comes up in output.
Script:
local B1 = script.Parent.Handle.B.B3
local A1 = script.Parent.Handle.A.A2
local Player = game.Players.LocalPlayer
local Mouse = Player:GetMouse()
Mouse.Button1Down:connect(function()
B1.Enabled = true
A1.Enabled = true
Mouse.Button1Up:connect(function()
B1.Enabled = false
A1.Enabled = false
end) ()
end)