Issue Description
AR1200V is PBX SIP server. One IP Phone connect to it, but customer finds he cannot make a call to remote site.
Handling Process
1. Check the configuration is ok. Let customer capture the packet.
2. From the captured packets, we find IP Phone can register to AR successfully. But there is an error AR router replied during the call.
The error code is 480 (Temporarily Unavailable)
3. According to the error, usually, it is because of the license.
4. Let customer check the license status. We find it has been expired. Generate a demo license and test it works fine.
