Why is the "wait()" method not allowing my script to run?

The reason your script seems like its stopping is because inside your for loop you have a wait(40) how for loops work is they go in order, they dont all happen at the same time, like itll to this, First lantern do this, wait this much then do this, on to the next lantern. It seems like its not working but it is. To fix this we can use the spawn() to make the code in the for loop run side by side to the for loop.

local light = script.Parent.LIGHT

script.Parent.ClickDetector.MouseClick:connect(function()
    script.Parent.Transparency = 1
    local la = game.Workspace.Lanterns
    local lag = la:GetChildren()
    for _,v in pairs (lag) do
	spawn(function()
	        if v.Name == "LanternAtt" then
	            local attA = v:FindFirstChild("AttachmentA")
	            if attA then
	                local at = attA:FindFirstChild("Attachment")
	                if at then
	                    light:Play()
	                    at:Destroy()
	                    wait(40)
	                    game.Workspace.Atmosphere.ParticleEmitter.Enabled = false
	                end
	            end
	        end
	end)
    end
    wait(100)
    for _,v in pairs (lag) do
        v:Destroy()
    end
end)