Model : Archer C5400

Hardware Version :

Firmware Version : 2.0

ISP : comcast

I know this has been discussed, but any solution? the 2.4 and 5 were working fine for about 1 week (this is my second RMA router) then the 2.4 stopped working. IT is showing up in all my devices but "no ip address" comes up and I cannot connect which is a pain because my printer and thermostat are only 2.4 compatible. Contacted support and a third RMA was recommended. Comcast and Arris also said their equipment is fine. I have flushed the DNS, reset the ipconfig under Command prompt, changed the channel and frequency to only 20 MHz, changed the network adapter settings to only 20 MHz, and NOTHING works. Why would it be ok for a few days and then stop working. Also it came with a June build , stopped working and I figured it needed that update in firmware to the Sept one , but it did not help.

Oh, and the current router does not show up on their system so I cannot even register it for the RMA :(

thanks