You need to make at least one call from Gmail, before GV will ring the OBi. You should exit Gmail and reboot the OBi before retesting.
If you've already tried that or it doesn't help, confirm that your GV settings changes are being saved, by closing all browser windows, then opening a new one and logging into GV.
Confirm that you are working with the right GV account. What you see under "Your number:" in the left frame of the GV settings page should match the caller ID sent when you call from the OBi.
If no luck, report whether attempted incoming calls appear in the OBi's Call History, and in GV's History.