SOLVED!I had the same cell phone that I'm forwarding calls to from GV listed in ObiTALK as a "Trusted Caller". So when I called home, it went through the Obi Attendant and rang and rang without Google Voicemail ever picking up. I DELETED my cell phone from the Trusted Caller list, then turned off and turned on my Obi 100. Boom, voicemail worked again. I tried the process again to see if it was repeatable, and it was. So that's the answer.
Stewart, Hero Member, I did try your *67 trick and it WORKED. It was kind of funny, as I was waiting for Google Voicemail to pick up, a mysterious "Unknown" caller was trying to call me at the same time! (Who could that have been?) I noticed that I wasn't going through the Obi Attendant, which is what made me stumble onto the solution. So thanks!
And, as for the other tests, when I tried calling my home line with the Obi turned off, I could reach voicemail and both make and receive calls from my computer.
Thanks for all your help! And that goes for pc44 and Rick as well! Cheers!
P.S. For anyone who stumbles onto this thread trying to figure out this stuff, I found this Google voicemail phone menu
Quick Reference Guide helpful.