Having a problem SSG5 with polycom HDX6000

Hi all,

I have configured SSG5 for VC polycom HDX6000.

I can call to some the remote side (I can see and hear any thing from them).

But for the only one remote side I cannot see and hear from them.

at the remote side also cannot see and hear from my side.

Althought, the connection of two side was established as I can only see the incoming call on mornitor.

As My configuration on SSG5:

- I set a MIP for Polycome at public interface in SSG5.

- Polycom has a private IP in trust zone. Then I set one policy for Polycom from trust zone to Internet with permit all service 

and one policy for Polycom from Internet to MIP also with permit all service.

please advice me the reason of trouble that I cannnot see and hear from only one side.

or reason of trouble come from the remote side.

Please help me.

Thank in advance.