Thanks.
Open a web browser, and log into only the one Google account you are using for Google Voice. Be certain that you are logged into the correct Google account, and not some other account you may also use. Leave that browser tab open. Press Ctrl-T to open another tab in the same web browser.
Log into your OBiTALK web portal account. Is your OBi listed there? If not, add it, using the **5 procedure.
Delete the Google Voice SPx completely (click the trash can icon). Wait a few minutes for the OBi to be remotely reset and rebooted by OBiTALK. Then, click on the SPx (e.g. SP1) you want to use for Google Voice, and go through the steps to configure Google Voice on the OBi. When it asks for your permission to use the Chat service on your Google account, make sure that the Gmail address it displays is the same as the one in the other browser tab. Complete the procedure.
Does it work now?