Unplug your OBiTALK device.
Use a laptop/desktop computer, running either Firefox or Google Chrome Browser.
Sign into the Google account that (presumably) holds your Google Voice number, and go here:
https://voice.google.com/settingsConfirm that you see your Google Voice number at the top of the page. If not, you either don't have a Google Voice number, or you're signed into the wrong Google account. IF you can't find it, stop here and reply.
If this is the correct account, with the correct Google Voice phone number, then scroll down the settings page. You should see an entry for "OBiTALK Device". If not, you didn't correctly complete the OBi / GV setup. Scroll down further and confirm that you again see "OBiTALK Device" in the inbound calls section.
If this is correct, then X out of settings and go to the "Calls" section (the little telephone handset). Click the "Make a call" button. Assuming your computer has a speaker and microphone or a headset, you should be able to make an outbound phone call over VoIP. Does that work? If not, stop and report back. If so, then have somebody call your Google Voice phone number from some other phone number. It should ring on your computer. Does that work?