Scheduling a procedure with DBMS_SCHEDULER. PLS-00103: Encountered the symbol “NULL” when expecting one of the following: ;
Most probably you are creating objects in different schemas,verify created jobs and job details in current schema with these views user_scheduler_jobs and user_scheduler_job_run_details
Simple procedure scheduled to run every 2 minutes
  SQL&gt;create or replace procedure test_print
      2  is
      3  begin
      4  dbms_output.put_line('Current date and time is : ' || to_char(sysdate,'DD-MON-YYYY HH:MI:SS AM'));
      5* end;
    SQL&gt; /
    
    Procedure created.
    
    SQL&gt; exec test_print();
    Current date and time is : 20-08-2020 09:22:59 PM
    
    PL/SQL procedure successfully completed.
    
    
    SQL&gt; BEGIN
      2             DBMS_SCHEDULER.CREATE_JOB (
      3              job_name =&gt; 'JOB_TEST',
      4              job_type =&gt; 'STORED_PROCEDURE',
      5              job_action =&gt; 'TEST_PRINT',
      6              number_of_arguments =&gt; 0,
      7              start_date =&gt; NULL,
      8              repeat_interval =&gt; 'FREQ=MINUTELY;INTERVAL=2;',
      9              end_date =&gt; NULL,
     10              enabled =&gt; FALSE,
     11              auto_drop =&gt; FALSE,
     12              comments =&gt; 'Testing job runs');
     13
     14
     15
     16
     17
     18              DBMS_SCHEDULER.enable(
     19               name =&gt; 'JOB_TEST');
     20  END;
     21  /
     
  SQL&gt; select job_name,output,status from user_scheduler_job_run_details
       2  where  job_name='JOB_TEST';

JOB_NAME   OUTPUT                                             STATUS
---------- -------------------------------------------------- ---------------
JOB_TEST   Current date and time is :20-08-2020 09:30:05 PM   SUCCEEDED
JOB_TEST   Current date and time is :20-08-2020 09:32:05 PM   SUCCEEDED
JOB_TEST   Current date and time is :20-08-2020 09:34:05 PM   SUCCEEDED
JOB_TEST   Current date and time is :20-08-2020 09:36:05 PM   SUCCEEDED
JOB_TEST   Current date and time is :20-08-2020 09:38:05 PM   SUCCEEDED
JOB_TEST   Current date and time is :20-08-2020 09:40:05 PM   SUCCEEDED
JOB_TEST   Current date and time is :20-08-2020 09:42:05 PM   SUCCEEDED
JOB_TEST   Current date and time is :20-08-2020 09:44:05 PM   SUCCEEDED
JOB_TEST   Current date and time is :20-08-2020 09:46:05 PM   SUCCEEDED
JOB_TEST   Current date and time is :20-08-2020 09:48:05 PM   SUCCEEDED
JOB_TEST   Current date and time is :20-AUG-2020 09:50:05 PM  SUCCEEDED -- Modified date format in procedure
JOB_TEST   Current date and time is :20-AUG-2020 09:52:05 PM  SUCCEEDED
JOB_TEST   Current date and time is :20-AUG-2020 09:54:05 PM  SUCCEEDED
JOB_TEST   Current date and time is :20-AUG-2020 09:58:05 PM  SUCCEEDED
JOB_TEST   Current date and time is :20-AUG-2020 10:02:05 PM  SUCCEEDED
JOB_TEST   Current date and time is :20-AUG-2020 10:04:05 PM  SUCCEEDED
JOB_TEST   Current date and time is :20-AUG-2020 09:56:05 PM  SUCCEEDED
JOB_TEST   Current date and time is :20-AUG-2020 10:00:05 PM  SUCCEEDED

18 rows selected.


SQL&gt; select job_name,last_start_date,last_run_duration from user_scheduler_jobs
  2  where job_name='JOB_TEST';

JOB_NAME   LAST_START_DATE                                    LAST_RUN_DURATION
---------- -------------------------------------------------- ------------------------------
JOB_TEST   20-AUG-20 10.08.05.070000 PM US/CENTRAL            +000000000 00:00:00.009000

Edit:- Just observation you were able to run job manually but not running from scheduler implies job and procedure are not in the same schema.