This error occurs when one or more features are rejected by the Create Routes process. A text file is created in the temporary file path to store information about those features. This file contains a full description of these issues.
Review the log file to examine the errors encountered during route creation to see how to proceed. One of the more common errors you might encounter is "The measure value is outside of the output M domain." This error occurs when an m-value being assigned to a route feature falls outside the allowable m-range as defined by the m-domain. To resolve this, ensure the m-domain defined for the output route feature class is appropriate for your data.