Assuming you have Google Voice as the only service provider and it's configured on SP1, verify you have the following settings in the OBi:
Voice Services -> SP1 service -> MWIEnable : (checked)
Voice Services -> SP1 service -> X_VMWIEnable : (checked)
Voice Services -> SP1 service -> MessageWaiting : (unchecked) (Default unchecked)
Do this by logging into the OBi directly at the IP address returned by dialing ***1.