Unable to close the POs with API po_actions.close_po

I am using below script to close the PO in program.

DECLARE

x_return_code varchar2(100);
x_returned BOOLEAN;
v_interface_run_id number;
v_phase VARCHAR2(25);
v_status VARCHAR2(25);
v_dev_phase VARCHAR2(25);
v_dev_status VARCHAR2(25);
v_message VARCHAR2(100);
v_request_id NUMBER;
v_success BOOLEAN;
po_close_cnt number := 0;
l_gl_cnt number := 0;

begin

DBMS_OUTPUT.PUT_LINE('Executing API');

mo_global.init('PO');

mo_global.set_policy_context('S', 31117);

DBMS_OUTPUT.PUT_LINE(

                  'Calling PO_Actions.close_po for Closing/Finally Closing PO =>');


x_returned := po_actions.close_po(p_docid         => 60000132,

                                  p_doctyp        => 'PO',

                                  p_docsubtyp     => 'STANDARD',