The topology could not be created. This error likely occurs if you try to overwrite an existing topology that is currently open in ArcMap or if the overwrite geoprocessing setting is set to false.
If the topology has been added to ArcMap, remove it and try again, or specify a new topology name. Also, check if the geoprocessing overwrite output option is set to true. To change this setting, click the Customize menu, click ArcMap Options, click the Geoprocessing tab, then check the option to Overwrite the output of geoprocessing operations.