C6300 Not Working

Hi, everybody~ I think I need you guys help. My modem&router doesn’t work these day. The model of my router is C6300, AC1750 WiFi Cable Modem Router.The front lights are all off, even the power one..but the rear side, lights are all on. I have already tried “reset ”many time, it is still like this. I bought in bestbuy just a few months before. It cost me over $180. I connected with Bestbuy before, they said it has been extended their return period, they cannot return or exchange for me. They suggested me to talk to the manufacturer directly. I will attach my router series number, and pictures of front and back. This is the router status with power on. And I don’t believe this is the adapter problem, because I bought the exactly same one from bestbuy. With new adapter, it is still not working. If this is product problem, how can I connect to customer service?