Cisco 7961G IP phone cannot registry to Asterisk server

Dear all

I tried to use Cisco 7961G connect to Asterisk at Raspberry pi. The phone 's firmware was refreshed to SIP version. However, it cannot registry to Asterisk (prompt “registering” long long time) . And the report page of FreePBX shown no online.

I had created the extension already.

I refer some guideline told remove everything between , so I remove “true” on the true. Now the section became:

Yes, the "registering " no longer prompt, but the report page of FreePBX still shown no online.

I tried to install a software SIP app in my notebook, and it sucess registry to Asterisk (show 1 online).

How to let the Asterisk server know the assigned Extension number for a Cisco 7061G IP phone ?

Thanks in advance.