Don't disable firmware updates. You need version 3.2.2 (Build: 5921EX).
Do this:
Go here:
https://www.obitalk.com/obinet/pg/obhdevCompletely delete the OBi device from your dashboard, and wait several minutes.
Then, unplug the OBi from power and Ethernet. Get a paper clip and straighten it out. Turn the OBi upside-down and find the small round bump with a hole in it. This is the recessed reset switch. Gently depress and hold down the switch with the paper clip. You'll feel a click. While holding it down, use your other hand to plug in just the power cord. Wait at least 10 seconds, then release the paper clip and turn the unit right-side-up. Wait until the power LED stops blinking - this will take several minutes.
Next, unplug the power cable, then plug in the Ethernet cable, then the power cable. Wait for it to fully reboot.
Now, follow the **5 xxxx procedure to add the device to your OBiTALK dashboard, then configure Google Voice. This should automatically upgrade the device's firmware and configure Google Voice properly.