Hello Belkis,
What are the 'GUI Configuration' settings of the service ZCATW in transaction SICF?
Following SAP Help site might be useful:
Setting Up the ICF Service for the ITS Service (IAC)
SAP Library: http://help.sap.com/erp2005_ehp_06/helpdata/en/4b/cc9000cf0450e9e10000000a15822b/frameset.htm
Regards,
Oisin