I want to clarify what you can, and can't do.
If you pickup your house phone and make a call, it works, correct? And GV is the ONLY service you configured with the OBi?
If someone calls your GV number, does your OBi ring the house phone? You said you can make and receive calls, so I'm not clear on what's not working.
Is the only issue that when you try to use your GV account on the web, and try to call your house phone, it doesn't ring? If so, be specific on what you are trying to do. If I go to the GV web interface, and tell it to call my GV number via Talk, my house phone rings and I hear Google telling me how to place a call, which is how it should work.