I have comcast cable internet run through a Motorola SBG900 cable modem/bridge then through my Telo and then through a Cisco EZXS55W switch and then out to computers, printers, etc. No wall landline is attached to the Telo.
Initially I would power on the entire system and although I had connectivity all the way through to my computer, the only thing I got with the Telo was a power on sequence where it lit up the 1/2, then the trash can and mail symbol, then the bottom four symbols and then the Ooma symbol started to flash (slowly at first and then picked up speed). It makes you think that everything is working fine and that maybe it is just downloading. But 10 hours later you realize something isn't right.
When you go to the http://setup.ooma.com/ page you'll see things that tell you Ooma Core and phone line are still trying to connect. Eventually I realized that I needed to go into my Motorola SBG900 and allow the Telo to bypass the firewall. I did this by adding the Telo's IP address (found on the http://setup.ooma.com/ page; mine ended in .13) to the SBG's DMZ page (http://192.168.0.1/,then login and then navigate to Gateway (on the left) and then LAN (on the top) and then DHCP Leases (also near the top). Once on that page, look at the bottom and ADD a DHCP lease (using information from the Telo page and selecting BYPASS. A few second later your Ooma should connect to the Internet and the lights will start rotating around. Eventually everything on the Ooma will light up with solid blue and you should have a dialtone when you pick up.