Web Services - Virtual Interface not found

Hi all,

I am experienced the following issue.

An external system calls SAP ECC 6.0 through some web services. The error that arise is "Virtual Interface not found".

This kinf of problem is not detected in every environment (i.e. not detected in Unit test environment/detected in Integration test environment).

We suspect there's some customization that need to be done.

Reading the wiki's about this issue, we are supposed to follow the steps:

--> SE80 --> Edit Object --> Enterprice Services --> click on Virtual Interface radio button.

In our system there's not a radio button with "Virtual Interface" label .

Any suggestions?

Thanks in advance.