RFC call failed while configure SSO between NW7.4 and ECC EPH6

Hi all,

I have a porblem while run t-code RZ70 (Gateway Host: portal_host name,  Gateway Service: sapgw00)

as follows：

"RFC data prepared

Used RFC destination: SLD_UC

RFC call failed: Error when opening an RFC connection (CPIC-CALL: 'ThSAPOCMINIT' : cmRc=2 thRc=67

I have done these steps:

1)  Set SSO parameters in the backend ABAP system ECC EHP6 by the t-code RZ11

2)  Add CA of EP into backend.

3) Create a "system" in EP and  finished OK.

     but show " Connection failed. Make sure user mapping is set correctly and all connection properties are correct. " while testing.

4) SLD Configuration

So, Can anyone tell me where the problem is taking place?

Thanks & Best Regards

M.H