Refer to the quick reference guide on page 20 of the user guide and the troubleshooting section on page 40.
Is your ooma hub configured to use a landline? If so, is there dialtone on the landline and is it plugged into the wall port of the ooma hub?
Are you able to connect to the internet (assuming you are since you posted here, unless you used another internet connection)?
You can try connecting to http://setup.ooma.com to see the status of the hub.
You may just need to reboot your modem, router and ooma hub by unplugging, wait 30 seconds and plug back in (one at a time starting with your modem).
I think that the hub is faulty...it has already been 1 day without phone service for me. I called tech support today, and they have to wait for engineering to get to me for a possible replacement. How many days will that be for me without phone service...
Turn it off. Turn it back on while holding down the blue/red ooma tab. (yes it is a switch)
Hold it down for about 30 seconds while it plays a red lightshow and does it's thing.
Hub should be reset to factory after that.
Also, pull out the network cable from ooma to your modem. Reset both connections just in case one pulled out. You may want to try a new cat 5 cable between them.
If the hub was provisioned to use a landline, a telephone must be plugged in the hub... even if I have all of the cables unhooked and just stick in the power to the hub, all th lights still blink...