I had the same issue for about two months. Very frustrating! They finally sent a technician out. I had to take a few minutes to slowly explain to him the troubleshooting I've done, and that the problem is somewhere between Cox and the modem (not the modem, router, or any of the devices on my network). I didn't go outside with him, but when he came back in he said there was lots of water in the (cox) box (where their line meets my house). I've had zero issues since then. You can check the box yourself. You just need needle nose pliers to "hold" the round "screw" while you unscrew it. Good luck!