求助, single stage dialing: Asterisk->obi#1->obi#2->pstn

freewilly

I'm able to do single stage dialing through both attached phone and AA
phone(attached to obi#1) -> obi#1 -> obi#2 -> pstn
by dialing <speed dial>*[dial out number]

But I failed to do the following with single stage dialing:
Sip client -> Asterisk -> obi#1-> obi#2 -> pstn

I can do single stage dialing with this setup
Sip client -> Asterisk -> obi#2 -> pstn
but for some reason, obi#2 reports "fail to connect to" Asterisk several times while there is no issue with obitalk, gv and network on obi#2.

obi#1.sp2 is connected to Asterisk, I simplify the setup of obi#1.sp2.X_InboundCallRoute to {pp(1*18335500)} for testing.
where "1" is the speed dial of obi#2. But obi#1 connect to obi#2.

Please help.