@Sunshine Hello. Thank you for all your advice. The firmware is the current version so it appears we've exhausted all options. I will contact the engineer on the email you've provided. Thank you

@Sunshine Hi. I have done a Factory reset now and the same problem continues on all devices. We get the message "Unable to connect" even though the devices can see the 5ghz channel.

@Sunshine Hi. Thank you again. I rebooted through the app. I also disconnected from power for a minute. Are these the same as Factory reset? If not, what is the correct procedure please?

@Sunshine Also, wired connection and 2.4ghz wireless working perfectly.

@Sunshine Hi. Thanks for the suggestions. Changed the name and password for the 5ghz channel but no connection. Changed from auto channel selection to 36. Again, no connection. Message continues to...

We've been using the Archer MR600 V2 as an NBN WIFI router very successfully for the last 6 months. We normally connect through the 5ghz channel because it is much faster than the 2.4ghz alternative....