[Chimera-users] slab representation of nucleic acid

The slab representation of nucleic acid under Depiction is not working. I made the following settings *show backbone as* atoms/bonds, *show sugar as* atoms/bonds, *show base* as slab. But the representation is not displayed on the screen. What could be the reason. I myself have used it before and i am not aware why this happens now. Regards, Bala