I'll be the first to admit that caller ID name is a big mystery with regard to Google Voice, and that I am likely mistaken. One thing I can confirm (confirmed via my GV engineering contact) is that the Google Voice apps and new web UI can display the name associated with the inbound number on VoIP calls, pulled from your contacts. (This is NOT the same as traditional CNAM LIDB lookup). Whether or not OBiTALK SIP clients now do that is debatable.
I could swear that the behavior worked as I describe earlier, and the fact that you're now reporting that the behavior has changed is even more mysterious. What makes this even more confusing is that Google's Pixel phones have their own caller ID name function (again, not via the CNAM LIDB).
Google Voice doesn't send caller ID name (in the usual CNAM PSTN format). The working theory is that OBiTALK users who have been seeing this have been getting it from OBiTALK, not from GV itself. In other words, if you subscribe(d) to OBiEXTRAS at one point in time, you would have authorized OBiTALK to import your Google contacts. I have no idea where they are stored with regard to using OBi ATAs (on the device's flash memory, perhaps). There was a brief period of time whereby this import feature was mistakenly enabled for everyone, for free. Perhaps this error was finally discovered and fixed, thus killing the name presentation. So, if an inbound call comes in, the name and number would be matched to that list, and the ATA would send it to the phone as standard CNAM. This is all speculation on my part, since nobody will say with authority.
Compare this to the OBi IP phones, which have the contacts import feature for free. In this scenario, the contacts are imported to the phone itself, so that's where the names are coming from. You can see this if you look at your Google account's app permissions. You would have granted (and perhaps later deleted) permission to OBiTALK to import your contacts.
If anyone has the time and energy to test this further, with a variety of calls from other GV numbers, non-GV numbers, and known business numbers (e.g. a local store or business), please feel free to report your findings.