I appreciate (really!) that you are patiently trying to help. Thanks.
My OBi202 is running the latest firmware, pushed by the portal at some unknown time in the past. I have not manually flashed that or any other firmware version.
Although I sometimes look at settings in the local web UI (for example, to view the call history or to see if something is actually in sync with the portal), it has been many moons since I made any changes locally.
I make all changes via the OBiTALK portal. True, I do sometimes make changes using the "expert" menu, but I have not made any changes there whatsoever to the SP configured for GV. In fact, the only changes I have made to the GV SP have been done with the non-expert menu and are as I have described: I have tried making trivial changes and saving (for example, changing which physical phone rings on an incoming call), and I have deleted and reconfigured the GV SP.
I stand ready to be chagrined when some change I make shoots me in the foot, and I know there are people around who are trying random things without really knowing what they are doing. However, in my case, the "service not configured" for GV happened on its own at least 12 hours after the last time I even looked in the direction of my OBi202, and at least 12 hours after it was working as expected. It's becoming more and more clear that OBiHAI did not handle recent changes very well and is just scrambling to catch up.
As a last resort (so far), I resolved my situation ... with no help from OBiHAI ... by deleting my OBi202 device from the portal and re-adding it. GV configured correctly within a few seconds of my clicking the buttons. Why I should have to do that or why it makes a difference will probably remain forever a mystery, because it's pretty clear that OBiHAI isn't saying much about anything.
Thanks again for having taken the time to respond, to me and to others.