New XFi Gateway Modem not connecting to internet - Green blinking light

Hello - before I start, I have checked the wires, I've tightened them (no luck), I've loosened them (no luck.) 

Yesterday I was setting up my new XFi Gateway Modem/Router. Previously, I have owned my own but it was time to upgrade so I went with the XFi Gateway. 

I have NEVER had an issue with the internet/coax cables. 

I started by activating my gateway, followed all of the instructions, and used the new coax cable that was sent with the gateway. I was able to get my internet set up and going but realized my TV was not working. I did small research and realized, Comcast only sent me a singular coax, and I needed the splitter for my cable box. I grabbed my old splitter, set up the wires, and turned my gateway back on. 

Except this time, no luck. Since last year, I have reset everything I possibly could, checked the wires, went back to the singular wire, tried an entirely new wire - nothing. 

The modem keeps blinking green. If I unplug the coax, it goes to a blinking yellow, telling me the coax is indeed on... but for some reason no internet. 

Please help!!