GE Water Softener repair

I have a GE GXSF27 water softener which had a leak in the brine tank, which required replacing the tubing assembly. The tubing assembly connects to the venturi body with a plastic ferrule nut, which I purchased from a local Sears outlet. Does the ferrule nut require any additional compression-type fittings? It doesn’t seem to be a secure connection with just the ferrule nut. The nut I replaced was cracked and glued in place by a previous owner, so I’m not sure if it’s missing any parts. The Operating Manual doesn’t show any other parts in the schematic other than the tubing and ferrule nut.