Good news, Hanky!!

I took a break and walked the dog. While doing so I was thinking about the issue and figured that the only thing that can click is the funky spring. I thought it must have been out of shape and pushing into the connector preventing the fingers to clip behind the ridge of the male connector. Your reply confirmed this.
Using needle nose pliers I bent all long fingers towards the outside and all little fingers toward the inside. I also spread the diameter a bit so it will lay to the walls of the female connector. Finally I heard the click when I connected the lines and they would not separate by hand.
I took the truck for a 15 minute test run and it stayed connected. I'll have to bleed it some more but that should be it.

Thank you so much for your input, Hanky!

 

It was quite a trip, if I only thought about it long enough I would have suggested you take the dog for a walk sooner! Thanks for the update, glad you figured it out and solved the problem.