Subnetwork trace fails with an error about missing or invalid parameters.

Workaround

As suggested by the Python errors, the geoprocessing tool is failing because the UN_Temp_Starting_Points and UN_Temp_Barriers feature classes are not created in the default geodatabase.

Under the Utility Network Data tab > Tools, click on Subnetwork. This opens the Trace tool and also creates the temporary tables in the default geodatabase. Now running the Trace tool completes without any issues.

Steps to Reproduce