When this edge was whole, I believe there was a blendsrf on the problem edge. It was partial and giving me problems. I split the edge to start over:
SplitEdgePreBug.3dm (95.1 KB)
I’m not sure if I deleted the blend before or after the split, but I was able to make a neighboring srf on the first segment. Now it shows two complete edges. BlendSrf couldn’t use it.
SplitEdgeBug.3dm (65.7 KB)