I am fairly certain that you are blocking something from Google. The most likely culprits are blocking cookies, or running a javascript blocker, or some upstream thing (firewall/content filter) that is blocking something.
You must not block any cookies from Google, anywhere in the path from your PC to your ISP.
Try this: open an incognito window, as I explained earlier. Sign into the one, and only one Gmail account (you
are using a consumer Gmail account, right?
Go here:
https://voice.google.com/settings. Do you see the Google Voice number you wish to use? Are you currently located within the USA? If you do see the number, then close (X) the settings and go to the calls page. Try making a call on your PC (over the Internet). Does that work? IF you had not already accepted the terms of use, then this won't work and you don't have a Google Voice number, and you can't use Google Voice with an OBiTALK device.