An unconfigured OBi at factory defaults with nothing connected but power and a telephone (to the PHONE Port) should have dialtone and be able to reach the Auto Attendant by dialing **0.
Connect only a telephone set (to the PHONE Port) and power. Reset the OBi to factory defaults by using a paperclip to hold the reset button accessible on the bottom (through the hole with a circle around it) depressed for at least 30 seconds. After releasing the reset button, give the OBi a couple of minutes to initialize. If dialtone is still not present, the problem is most lilely a defective telephone, connecting cord, or the OBi itself.