A powered OBi should always give dial tone. It doesn't need configuration to do that. It doesn't even need a network connection to give dial tone.
No dial tone usually means a hardware failure, usually of the phone cord or phone itself but sometimes the OBi's phone port circuitry. Check the cord and phone by substitution or by plugging them into a known working PSTN/POTS socket.
If they prove OK, log in to the on-board management interface (not the OBitalk portal). click on Status and then on Phone Status. What, if any, numbers do you see for the voltage readings?