G34 how to do a warranty exchange??

My Arris G34 has been deemed defective by Xfinity. Their technician checked all of my cables inside and outside and they all have strong signal. The Surfboards light is green and flickering and there is no wifi available.  My warranty runs out Feb 28th, 2024. I need to get this done quickly, as I also have no security system because of this and there's been a lot of break-ins and thefts in my neighborhood recently.