So, the device itself is offline, which has to be diagnosed before even thinking about Google Voice.
Pick up the phone and key in ***1. It should read back its IP address. If it doesn't, you have a LAN issue. If it does, then enter that address in a web browser, and sign into your OBi. The default user ID and password are both admin.
Can you get that far? If so, look at Status-->System Status, and confirm that it got a DNS address, and scroll down to the bottom of the page. What does it say in the OBiTALK Service Status?
Did you previously follow instructions someone posted on this or another forum to disable anything OBiTALK-related on your device?
If the device gets an IP address, but OBiTALK service is dead, you may want to try a factory restore on the device. First, delete it completely off of your OBiTALK dashboard. Then, pick up the phone and key in ***8 then 1 to factory reset it, and give it plenty of time to reset. Then, pick up the phone and key in **9 222 222 222 and listen to determine if you hear the "Welcome to OBiTALK..." prompt?