Well, you installed a 12-year-old cable modem/router, for starters. All bets are off as to compatibility. It's not even worth troubleshooting; it wasn't much good when it was new.
If you have an OBi 100 or 110, then you
must read and follow the instructions here to upgrade it:
http://www.obitalk.com/forum/index.php?topic=11384.0If you can't afford to buy or lease a current-generation cable modem, then take your OBi to a friend or family member's house and try setting it up on their network, before wasting any more time with that old modem/router.
Log into the OBiTALK portal page. Delete the device completely off of the portal. Wait a few minutes. Then, pick up the phone attached to the OBi and press ***8, then press 1 to factory-reset it. Wait long enough for the LEDs to stop blinking; at least 5 minutes.
Add the device back to the OBiTALK portal using the **5 method. If this works, then you can set up Google Voice by following my instructions, here:
http://www.obitalk.com/forum/index.php?topic=8560.msg56460#msg56460