If you previously disabled OBiTALK provisioning, that could be the issue, but I doubt it. Another possibility might be if your Anveo configuration somehow locked down something, or changed something, that is interfering with Google Voice setup.
At this point, I'm going to recommend that you log into the OBiTALK dashboard, and click the button to completely delete your OBi off of your portal page. Wait a few minutes while the LEDs blink and the device resets. Then, unplug all the cords from the OBi to power it down. Plug in the phone and power cords, not the Ethernet cable. After it boots up, pick up the phone and key in ***8 then 1 to restore it to factory defaults.
Meanwhile, open open an "incognito" or "private browsing" session on your browser (Ctrl-Shift-N for Google Chrome Browser, or Ctrl-Shift-P for Firefox or MSIE). Log into only the one Google account that you're using with your OBi, and no others. Press Ctrl-T to open another tab in that private window, and log back into the OBiTALK portal.
After the 202 chews on that factory restore for a good long time and finishes rebooting, then use the **5 procedure to add it back to your portal page, then set up Google Voice and see what happens (do this before attempting to set up Anveo again). Don't make any manual or expert mode changes.