Possible cause of the error (ORA-31626: job does not exist)
This error normally occurs when we do not specify a unique JOB_NAME for the Data Pump job and for some reason that JOB_NAME already exists in the database, or else if we are running many jobs at the same time (more than 99 jobs) and Data Pump cannot create a new job.
To fix this issue we have to cleanup the orphaned data pump jobs.
If we have left over jobs due to failures, simply issue a drop table statement. From the data pump jobs view, we can get the schema and the owner of the table. Then just issue a drop of that table
drop table "schema"."table_name";
Determine the data pump jobs which exists in the database and the status as NOT RUNNING:
SELECT owner_name, job_name, operation, job_mode,state, attached_sessions FROM dba_datapump_jobs where state='NOT RUNNING';