Attempts to add a print service in Portal for ArcGIS fail with the following error message returned:
Error: The print service URL you have entered is configured for Asynchronous execution. A print service configured for Synchronous execution is required.
The print service is configured or published as an asynchronous service.
To prevent this error from returning when creating a new print service in ArcGIS Pro, set the Execution Mode to Synchronous before publishing the print service to ArcGIS Enterprise. Refer to ArcGIS Enterprise: Share a printing web tool to the ArcGIS Enterprise portal for instructions.