Okay, here's what I'm working with. A late model aluminum master cylinder. The front port doesn't want to seal. Previously, with the original lines, it sealed fine.
I added an adjustable proportioning valve and had a local shop flare me a new line to attach to the front port. It didn't look quite right, but they assured me it would work. It leaked.
I decided to get rid of the line they flared and install an adapter fitting for the port and run a pre-made line out of it. It's still leaking.

So, I'm thinking their flare boogered up the male side in the master cylinder and it won't seal now. Are there any tricks "re-form" it? Or do I need to get a new master?

Thanks for any help. This is supremely frustrating.

check the condition of the MC cone seat. either it or the mating inverted flare male fitting that mates to the cone or if on this deal the line is flared & is what seats on the cone, one of the two is messed up. Some one several days ago posted a site for new cone seats

Just watched a video on how to replace those seats. Looks pretty simple.
I just searched here and with Google and can't find a source for these seats.
Anyone have a source?

Thanks.

Raybestos m/c rebuild kits come with them. Try RockAuto.

I've had some on my home-made double flares fail to seal (cheap flaring tool) until I purposely over-tightened the tube nuts to reshape the flare cone on a fitting. I use a couple of sacrificial fittings to reshape the cone and then throw them away.