Your ego is getting in the way of solving the problem. I neither work for Polycom, nor do I contest that their documentation is outdated. However, if you read through this forum, you'll find a very large number of users who followed
my instructions got their products to work.
My point was: you made an invalid assertion: the instructions are out of date, therefore the company may be abandoning the product. In truth, Obihai has always had crappy documentation, but the products have always worked as intended.
You repeatedly referred to your expertise in SIP. Google Voice is not configured like other SIP clients. Having many years of telecom experience is irrelevant, if you don't know the details of the particular service you are using. As DrGeoff pointed out, you have demonstrated that you don't understand how OBiTALK devices work.
Now: Google has completely replaced the Google Voice infrastructure in the past year. They have now introduced an enterprise (paid) version of Google Voice via G Suite, currently in an early adopter phase for customers with 100+ seats. Google is investing many millions of dollars in the service, and it is not going away any time soon. Whatever may have worked in the now-useless OBiTALK website instructions, which refer to the old Google Voice infrastructure, is irrelevant. Google now has specifically-dedicated server resources, tested and verified to work with OBiTALK devices.
It is an undisputed fact that OBiTALK devices running the latest firmware work properly with the latest generation of Google Voice. IF an OBiTALK device can successfully make and receive calls using a generic SIP ITSP such as Callcentric (thus proving that the hardware is not damaged/defective), THEN it will successfully make and receive calls when used with Google Voice.
We can't tell from your post what other tests you may or may not have performed. For example:
- Did you try making a call to the OBiTALK echo test server (**9 222 222 222)? This tests round-trip function, including sending and receiving audio.
- Did you try configuring the device with some other service provider and then making test calls? In your post, you described your use case as "just for some outbound calling for SIP testing on my enterprise phone system". You certainly do not need Google Voice for that testing; any ITSP will do.
- Did you test your Google account's Google Voice function without the OBiTALK device, by making and receiving calls either on the Google Voice or Hangouts websites, or via the Android or iOS apps?
You asked about troubleshooting steps. Try the above tests.