In all the time that I've been a member here, nearly a year, I do not recall a single complaint about ftp failures.
In any case, no one can give you any advice until you describe just how you've connected your modem and router and Ooma device and computer.
1. Try connecting the Ooma Telo behind (LAN side of) the router, by connecting to one of the four router ports to the Ooma Telo Internet port. (Modem-Router-Ooma Telo). Plug nothing into the Ooma Telo Home port.
a. Temporarily access your Ooma Telo home port by plugging in a patch (network) cable from the Ooma Telo “home port” to a computer’s network card port. Sometimes you have to restart your computer after installing the patch cable, so that a proper connection occurs.
b. Type http://setup.ooma.com in you browser address window and hit enter. The “Ooma Setup” window opens.
c. In the left hand Navigation window, select “Network”.
d. Under “Network Settings” go to network connection: select the down arrow with your mouse and select “Automatic” (if not already selected).
e. Enter the following:
i. Under “Modem Port MAC Address”, select “Use Built in”:
ii. Select the Update button.
f. Do a “cold boot” of the router.
g. After the router cold boot, do a “cold boot” of the Ooma Telo.
Try it and good luck.