This tool uses functionality in the ArcGIS Network Analyst extension. You do not seem to have a license for the Network Analyst extension or it has not been enabled.
Find an alternative approach to your analysis or purchase a license for the Network Analyst extension.
From within the application, click Licensing from the Catalog pane. Verify that Network Analyst is in the list of Installed Extensions. If Network Analyst is available in the list of extensions, but is unavailable, the license has not been activated. If Network Analyst does not appear in the list of extensions, it must be installed. See the administrator of your organization for more information.