This has absolutely, positively nothing whatsoever, not at all, in no way, uh-uh, to do with Google "pulling the plug". Google has no idea what model of OBi you are using, nor how long you've been using it, nor do they care, as long as your device is using OAUTH 2.0 authentication.
If it had been one user reporting this, then it would have been the now-tiresome answer: your OBi hasn't been updated in years, it's still using the old, pre-OAUTH authentication, and you need to upgrade firmware, reset the device and re-configure Google Voice on a SPx.
However, this is apparently happening to 100/110 models that are running current firmware and are using OAUTH authentication.
It looks like there's a problem with the OAUTH keys that are being generated for these models (a Obihai problem), and nothing more. I'm going to see what I can find out, but if any of you have a device under warranty, please open a ticket and point to this thread.