Sometimes you will meet issue that the output item remains in status ‘To Be Output’ in billing document when using new output management, that means the output item has been determined successfully but something happened during output processing so that the status could not be changed to ‘Completed’ or ‘ Error’.
There are several known reasons for why this kind of issue happened.
1)There is no supervisor destination or inbound destination defined.
Please open transaction sbgrfcconf to check whether supervisor destination or inbound destination defined or not.
This is mentioned in note 2292571 – SAP S/4HANA output control – technical setup
2)The customizing is incomplete for SOMU(Output Management Utilities on S/4HANA scenario).
The solution is mentioned in KBA 2462673 – Output remains with ‘To be output’ status.
3)The printer spool device is not PDF device types.
This could be checked by using transaction SPAD -> input the printer used -> check the device type.
Printer Spool Devices supported by new output management is restricted to only PDF device types (PDFUC : PDF Unicode 1.3 / PDF1 : PDF ISO Latin1 4.60+).
This is mentioned by Symptom part in note 2684805 – Supported PDF printer spool devices.
So far I only meet the above reasons which are mainly on incorrect customizing cause this kind of issue.
If the issue doesn’t belongs to any of above reasons,
then you may check in transaction sbgrfcmon to see whether the output request item has been sent to inbound destination set in transaction sbgrfcconf.
The processing error message could be found there, or check the processing log for the output item in billing document.