Troubleshooting: Why does ArcFM tell me it cannot find an edge feature when I place my flag on a line?
Usually this occurs because you have the incorrect geometric network selected on the Network Analyst toolbar. If you have two or more networks in your map, ensure that the appropriate network is selected for the trace you are attempting to perform.
For example, assume you have underground and overhead networks in your map. If you have the underground network selected and are attempting to trace an overhead line, the trace will fail because it is using the incorrect network. Select the overhead network on the Network Analyst toolbar and your trace will work.