Nighthawk RAX45 Stopped Broadcasting Wifi

Which WiFi channels are you using?

Also which region is the router from?

One potential issue that can make it seem like the WiFi SSID is disappearing, is if a DFS event has taken place. For example, if using the lower channels, then some of the channel width will fall within the DFS range, and the router will not do an 80+80MHz split, thus it could end up with the entire channel block being pushed into the DFS range. When in that range, you cannot actively probe for WiFi networks thus it takes a while to scan for them.

To rule out that issue, assuming a north American unit as a short term test (since this will reduce performance a little), Head to the router page.

In the WiFi settings, change the WiFi speed setting for the 5GHz radio from "Up to 4800 Mbps" to "Up to  2400 Mbps". After that, change the WiFi channel to 149 (or any non DFS channel for your region).

For the 2.4GHz radio, simply pick a channel manually instead of having it on auto.

If needed after applying the change, you can check which channels are being used by the WiFi radio. If they are not DFS channels, then use it like that for a while to see if the issue happens again.