So it sounds like you've now got Google Voice working without Obi in the picture at all, and you've also configured Google Voice to forward your calls to Google Chat as required. Yet you are not able to make and receive calls via the Obi. So at this point few more things to check:
1. Without considering GV at all, have you dialed the Obi echo test number from your Obi and verified that the device is working?
2. If the Obi is working, does the ObiTalk dashboard show that GV is configured on the selected line (say SP1?)
3. How are you dialing a number? If GV is not set up as your primary dial-out line, you will need to use the prefix **1 (for SP1). If it is set up as your primary line to dial-out then you don't need the prefix.
4. Are you able to receive incoming calls to your GV number on your Obi?
You also gave some new information that your set up worked once, but it doesn't work now. So let me ask you, have you updated your firmware and authorized and authenticated yourself with GV recently?