When the ArcGIS GIS Server PrintingTools service is configured as an ArcGIS Online utility service for printing, the first print request fails whereas subsequent requests are successful.
Reference the print task over port 6080 by adding all the ArcGIS GIS Server services to the web map through the ArcGIS Web Adaptor with the instance name ‘arcgis’. Use both the print task and the services added to the web map over the same web adaptor instance.