Need to be able tracing into the inside of the encapulated assertion to find where the request failed or get more debug detail information.
ssg 11.x
Need to set property values to enable debug into encaptulated assertion
To enable debug tracing, you must select the "Enable debug policy tracing" check box in the [General] tab of the published service's properties
Select Allow debug tracing into backing policy if you want to include the underlying policy fragment (includes encapulated assertion) during debug tracing; otherwise the backing policy is invisible to the trace.
Encapsulated assertions can be stepped into in the Service Debugger window.
In the policy manager Preference window, it has an option: Enable Encapsulated Assertion Debugging
Select this setting to enable or disable Encapsulated Assertion Debugging. The default mode of this flag is 'Disabled'.
When you debug a service/policy. Set brake point in a policy before or at the assertion that included fragment or encapulated assertion, and click "step into" to bring the tracing into the encaptulated assertion fragment.
The Enable Encapsulated Assertion Debugging option only available in ssg 11.x.