I think the default digit maps will accept anything that does not start with 911 (and maybe even that is not part of the default), as long as you wait -- I think it is about 10 seconds. You could hurry that by pressing # after your digits are in.
I wonder if your router or your Internet provider is blocking you somehow. I would connect the OBi directly to your modem for testing, if you have a separate router. If the modem and router are all-in-one, your could try putting the OBi into the DMZ for testing.
Once you are able to receive calls one way or the other, you can use a more precision approach.
If that does not get things working, I would ask
sipme.me for help if no fellow customers come by with a cure.