Guys: if you want to use Google Voice with an OBi device, "don't fight the power": use the OBiTALK portal to update to the latest firmware and manage the service provider slots. This method is required to use Google Voice with OBi devices. Trying to hack this on the local web interface is just going to cause a mess, and a potential security exposure, and there is no good reason to use a downlevel release of firmware at this time. The "I hate the portal and how dare Obihai update my firmware" attitude is really no longer realistic. The firmware is solid.
Do this:
Open your web browser. Log into the Google account you want to use with GV and your OBi (by "log in", I mean sign into any Google app, such as Gmail or Google Voice or Hangouts, so that your browser's session cookies are showing Google that you are logged into the account).
Open a separate browser tab (Ctrl-T), and on that tab, log into your OBiTALK portal page. If you have an existing GV service provider slot defined on your OBi device, delete it, and wait for the OBi device to be remotely rebooted. Then, add the GV service provider again. When you go through the procedure, it will use OAUTH 2.0 to authenticate to your GV account. This will pop up a window, from your Google account, and it will ask you to approve giving OBiTALK permission for offline access to your account. Once you do that, the OBiTALK provisioning system will go through the authentication process with Google, and it will automatically download the necessary firmware to your device, if it's not already installed. You will see a spinner icon while this is happening. You can't make this work properly without using the portal.
Seriously: don't try to hack this. Just follow the procedure if you want to use GV. If you are intent on using the local portal, you can disable updates AFTER you complete this procedure, but you will need to enable it again the next time you need to change your Google Voice configuration, so don't forget that the portal will over-write any futzing you did on the local web page.