Whats the error in the request log?
Looks like the PL SQL Function/Procedure which you are calling in the report trigger is going into some exception.
You may check OPP log for the same using the below query
SELECT fcpp.concurrent_request_id req_id, fcp.node_name, fcp.logfile_name
FROM fnd_conc_pp_actions fcpp, fnd_concurrent_processes fcp
WHERE fcpp.processor_id = fcp.concurrent_process_id
AND fcpp.action_type = 6
AND fcpp.concurrent_request_id = &&request_id
You can handle this in your function so that it always returns a value or handle the exception in the data definition. You can refer to below community threads for more details
The query is not returning a value. I have checked the OPP log , since the OPP is not called the OPP log has nothing for the request.
Can you examine the code you have written inside "after report trigger". That might be the cause.