Leaking from 3rd level arm between tub and insulation

Firstly thanks for reading! I did some poking around but couldnt find specific problem. I took my dishwasher apart for a major cleaning as she was all “bunged up” so I cleaned everything nicely, however when I put everything together and tested it I had excellent pressure but I cant get a good seal between the “coupler” (clear plastic snap ring to hold 3rd level arm on) and the plastic/rubber supply line elbow that brings the water in at the top of the tub. I unscrewed the arm assembley from the top of the tub and now it leaks between tub and insulation and down to the floor. Did i miss a gasket/washer that goes in threre? or can I use plumbers putty or silicone or??? any help is greatly appreciated…Thanks!

ok so I should have used the noggin befor posting I grabbed an old washer hose from the garage and pulled the black washer out and sanwiched that between the supply line on the inside of the tub and clear plastic “coupler” and low and behold it worked! I hope this post might help someone along the way with the same issue…Cheers! N.B. - A bead of sillycone (ha ha) wouldnt hurt either around the supply hose elbow and the outside of the dishwasher tub…should be ace after that!