Hi jvz,
Thanks for you reply. The advice of looking the "error log" was good. I didn't notice it before, but it clearly infroms what was wrong. The reason in this case was only a mistyped password for the certificate.
In this case the code obviously starts to create the security element, but stops the creation when an error occurs. It will not show information in the SOAP, but then if you go and see the log, it informs that an error has happened. Maybe there could be some kind of indicator to point out that please look the error log.
Thanks again for your help.