Great. So, now it is working properly with Google Voice.
There are two reasons to also use Callcentric: Caller ID name (CNAM) and E911. CNAM really isn't that useful any more. There are so many robocalls with spoofed caller ID numbers, that the names are meaningless. But, if you insist, then do this:
Assumptions: you already have a Callcentric account, with a Callcentric number (e.g. 17771234567). CC sells inbound calling and outbound calling separately. For CNAM, you need to obtain an inbound phone number from them (known as a "DID"). This can be one of their $1/month NY State numbers, which have unlimited inbound calling. For E911, you need to subscribe to outbound calling. I suggest signing up for their North America Basic plan:
https://www.callcentric.com/rate/plans/north_america_basic/, which provides both E911 and some outbound calling minutes just in case you need them.
Set up the DID number on Callcentric's dashboard, as an extension, on the "Extensions" page. You'll need to add a SIP password, which is not necessarily the same as the CC account password. Go to the "Preferences" section and click on the Voicemail tab, then click edit. Change the ring period to 30 seconds.
Click on the SP2 configuration slot on the OBiTALK dashboard. On the next page, decline the offer to set up Google Voice on this SP. Scroll down to the bottom of the page and click the "OBiTALK compatible service providers" link. On the next page, fill in your Callcentric 1777xxxxxxx number and SIP password and submit. Wait, and then SP2 should say "Registered". Test inbound calling and outbound calling to and from that number to some unrelated phone number. Fill in the E911 information and submit.
Does the CC DID number properly make and answer calls now? If not, stop and reply. If so,
Go to the Google Voice settings page and add your CC DID number as a linked number and enable it to ring on inbound calls. Toggle off the ringing to the OBiTALK device. Test it. You're done.