Getting error while launching Demantra from ASCP Concurrent Program

Hi

I am trying to run below script using pl/sql to launch demantra workflow using Concurrent Program:

SELECT utl_http.request('''||l_url||'/WorkflowServer?action=run_proc'||'&'||'user='||l_user_name||'&'||'password='||l_password||'&'||'schema='|| replace(l_wf_name, ' ', '%20')||'&'||'sync=no'') FROM dual';

I am getting below error:

RA-29273: HTTP request failed
ORA-06512: at "SYS.UTL_HTTP", line 1720
ORA-12545: Connect failed because target host or object does not exist

Please suggest.

Thanks in Advance