unable to modify task from queued to pending

Hi,
I am facing the error 'INVALD TASK STATUS' while modifying the task status from queued status to pending status by using the wms_task_mgmt_pub.modify_task

with the follwoing code

CREATE OR REPLACE procedure pr_taskupdate_to_pending(p_task in number,P_ERROR_MSG OUT VARCHAR2,P_ERROR_CODE OUT NUMBER)is
l_updated_tasks                WMS_TASK_MGMT_PUB.task_tab_type;
l_return_status                  VARCHAR2(10);
l_msg_count                      NUMBER;
l_msg_data                       VARCHAR2(200);
l_task_table                      WMS_TASK_MGMT_PUB.task_tab_type;
l_task_id                           NUMBER;
l_transaction_number        NUMBER;
v_transaction_number      number;