Is there a separate router in your network? If so, post make, model, how connected, any special settings.
Is your cable modem also a router? Make / model? (If your modem has only one Ethernet port and does not have Wi-Fi, it's not a router.)
Do you have business Internet service with multiple IP addresses?
If you have no router and a consumer Internet service, the OBi will not work in your system, because it and your computer would each need their own IP addresses, but the ISP provides only one. If this is your situation, you can test by disconnecting both power and Ethernet to your cable modem. Wait 30 seconds, power up the modem and wait for it to come ready. Then, connect the OBi to the modem and power it up. It should get an IP address and the power light should stop blinking. To get the modem working with your computer again, you will need to cycle the modem power once more.