44ad presumptive basis

If before fy 16-17 we have filed return on presumptive basis but for fy 16-17 we have filed on normal basis then can we go for 44ad again in fy 17-18 restriction of 5 yr is introduced by finance act 2016 so it should be possible to file again in 44Ad but everyone is denying why? Because finance act amendmend are on prospective basis not on retrospective basis