Try increasing RingDelay for the LINE port from 4000 to e.g. 6000. If no luck, report what, if anything, gets logged in Call History for name and number on failed calls.
If you just want outbound volume control, Ooma support can make the adjustment in the Telo, so you wouldn't need the OBi. Of course, there are many other reasons why Ooma and OBi make a good combination, e.g. to get better international rates, to get virtual numbers from other countries, to interoperate with iNum, SIPBroker, etc.