Description
The user running the Find Routes tool available with the ArcGIS Online route service does not have privileges to perform optimized routing; that is, they do not have privileges to use the Reorder Stops to Find Optimal Routes parameter.
Solution
If you are using an API key to run the ArcGIS Online route service asynchronously, ensure that the API key has access to the optimized routing location service, or uncheck the Reorder Stops to Find Optimal Routes parameter.