My family have been using obi100 for quite a while in Sichuan. My experience back one month ago and even earlier was that, as others said, it really depends on your Internet service provider. So it may become to work if you switch to another provider.
However starting from sometime in December, that obi100 stoped to register with GV and I saw the same message as OP posted. My guess is that this is related to the recent report of blocking gmail in China. It was about the same time. If it's the case, this is beyond your service provider, GV, and OBI.
As a result, we now only use obitalk network to make connections, which is not quite stable as GV previously.
You can of course set up some SIP on your obi100, but again this depends upon your ISP and your router. It may or may not work.