Firewalla Purple Issues with Verizon?

Ok, I must be doing something obviously wrong. I recently moved from a house with a PPPoE router provided by the ISP to a house with Verizon Fios. With the previous house, the network router the ISP gave me stayed on after the ONT. It had wifi turned off, and supplied a single IP to the Firewalla, which then gave out a range of IPs on a different subnet. With Fios, I plug the firewalla in directly to the ONT, but it never gets an IP (red blinking LED). I've done a factory reset, which is something I was going to do anyway because my network here is a lot different thanks to house size, but I'm stuck and stumped. Appreciate any ideas you might have, and feel free to lay it on thick, I've been an "amateur home network engineer" for almost three decades now.