I have a geometric network stored in an ArcGIS 10.5 geodatabase. These lines represent all the river paths in a watershed. The lines associated with this network have the required flow direction assigned based on line digitized directions. I can manually select an end node of one stream and use the trace geometric network tool in ArcToolbox to select a single upstream path without error. My network branches and I want to select an end node and return all the connected streams that flow to that end node. If I change the parameter to Find Common Ancestors the tool returns an error 001191: No flag found from the flag junction feature class. Ultimately I need to generate a Python script to select each nodes and select all upstream line segments but I cannot make the tool work. The inputted river lines, and the end nodes from those lines each share a CRS and reside in the same feature database feature class items.
If I use the Utilities Network Toolbar I can place a flag at an end and trace a single path like the image above. The same tools that fail using the Trace Geometric Network tool in toolbox are also grayed out in the Utilities Network Toolbar.
Is there a bug in the Find Common Ancestors parameter of the Trace Geometric Network tool?