[mr48chev]

Is that line just the way the flash hit it or is there a mark on the seat?

I see a tiny bit of dirt on the seat in the valve plus what may be uneven marks. That dirt may be enough to cause a leak.

The flare looks pretty good but I'd check it for being absolutely square from one side to the other, My old SnapOn flare tool that I have had for 50 years finally got tired and I was getting flares that looked ok but wouldn't seal on brakes.