JSchuricht wrote:Thanks. This is only when I tighten the nut. It sits flush by hand. Single oring in the groove

Hmmm- your O-ring channel is shallower than the one pictured on my Frontier in my earlier post. The Frontier O-ring stays in its channel and seals around its sides to the cylinder that it fits in. If your channel goes all the way back to the fitting, then it seals mostly on its sides.
So question is: does your "channel" extend all the way back (under the O-ring) ? Can you post a photo without that O-ring ? If your O-ring does seal on its sides, maybe a slightly-narrower O-ring would work. You'd need to look for a different size green refrigeration O-ring at NAPA or Carquest or similar, in the little drawers.
For one of my former vehicles (believe it was my 1994 Suburban, I had purchased a new accumulator which did fit, but the supplied O-rings were different thickness than the old ones, so I purchased ones at Carquest same size as the previous ones.