Larian Studios Forums Divinity: Original Sin 2 - The Modding Dungeon Divinity - Original Sin 2 - Modding Guides Tutorial - Implementing a Basic Quest (WIP)

That means that you have a node with exits that either do not connect to other nodes, or that connect to other nodes with flag or tag checks that cannot be satisfied.

The most likely case is that you did not mark a final node as "end node".