Update of CLOB column issue

Question

I am not sure if this is the correct forum for this question, so please forgive if this is posted in wrong forum.
I am new to working with CLOBs in Oracle. The procedure updates a CLOB column which stores large XML files. The XML files are first moved to the /u04 directory, then we execute the procedure which looks for the XML in /u04, then uses those XML files to update the CLOB column.
The procure works fine in our development environment, but doesn't work in our System Test box. No exceptions are thrown in Sys Test, but when we check the CLOB column it's NULL/empty.
Both Dev and Sys Test environments are on the same physical server.
Is there something in the database setup I should be looking for which may cause this difference in functionality?
Code is below. I'm sure it could be better but this is my first go-around with CLOBs.
Any help is greatly appreciated!
  --open CLOB used to clear out old XML in CLOB column
   dbms_lob.open(v_pre_clob, dbms_lob.lob_readwrite);
   -- prep XML CLOB column for update
   UPDATE REPORT_TBL
      SET REPORT_XML = v_pre_clob
    WHERE REPORT_ID = p_rep_id;
   --Close pre-update CLOB
   dbms_lob.close(v_pre_clob);
   --get a reference to the XML CLOB that needs to be updated
   select report_xml
     into v_clob
     from report_tbl
    where report_id = p_rep_id for update;   
   --open the target CLOB and source report xml file in /u04
   dbms_lob.open(v_clob, dbms_lob.lob_readwrite);
   dbms_lob.open(v_report_xml_file);
   --Load the contents of the xml file in /u04 into the CLOB column
   dbms_lob.loadclobfromfile(v_clob, v_xml_file,
                             dbms_lob.lobmaxsize,
                             v_destination_offset, v_source_offset,
                             nls_charset_id('US7ASCII'),
                             v_language_context, v_warning_message);
   --Check for the only possible warning message.
   if v_warning_message = dbms_lob.warn_inconvertible_char then
        dbms_output.put_line('Warning! Some characters couldn''t be converted.');  
   end if;
   --Close both LOBs
   dbms_lob.close(v_clob);
   dbms_lob.close(v_xml_file);
   null;
   EXCEPTION
      WHEN OTHERS THEN
         v_return_code := SQLCODE;
         v_return_mesg := SQLERRM;
         DBMS_OUTPUT.PUT_LINE('PROCEDURE update_xml_from_file');
         DBMS_OUTPUT.PUT_LINE('RETURN_CODE = ' || v_return_code);
         DBMS_OUTPUT.PUT_LINE('RETURN_MESG = ' || v_return_mesg);

Answer 1

Sorry, pulled that code from development where it was working.
The issue was the GRANT on the /u04 directory.