So, no dialtone when you plug in a phone to the OBi 200 and pick up the handset?
Perhaps you have a problem upstream on your network, between your ISP and the OBi, such as your modem/router/switch. Power everything off, wait 5 minutes, the power everything on again, starting with the modem, router and optional switch. Wait for each thing to reboot before powering up the next thing.
Turn the OBi 200 upside-down. Unplug all the cables. Using a straightened paper clip, gently press it into the hole in the middle of the small circular bump, until you feel a click. Now, while holding that down with one hand, plug in only the OBi's power cord, wait 10 seconds, release the paper clip and turn it over. It should now go through a factory defaults restore and you should be able to plug in a phone and get a dial tone, even without an Internet connection. If not, it's defective. If so, then plug in the Ethernet cable, power-cycle the OBi again, and see if it gets an IP address.