I have a basic Roku Premiere Model 3920X, Serial number: YH0037847034. My internet connection modem is thru Xfinity Arris Model TG1682G. It runs both 2.4 & 5 GHz. The network channel is 36. Everything was working fine until a powerful lightning strike that caused no more than 30 seconds of power outage. Since then, my Roku indicates that it is not connected on the home screen. I have unplugged both the modem & the Roku several times. I have restarted both devices several times. Even turned off & unplugged the tv. lol. I am at a loss. I have tried resetting the network connection. Manually entered the information, also. Double checked to be sure that I had been using the correct password. I have read thru all of the suggestions & cannot seem to resolve the issue. I restarted the devices in the order recommended. Please help.
My wifi is Both 2.4 and 5 GHz. I have been using the same modem (set at channel 36) and Roku Premiere together for several months. There have been no issues with internet connection until the power outage. Not sure where to find the wireless mode on my modem (no separate router). This issue literally JUST started after the lightning caused the power to go out momentarily.
As @renojim indicated, your Premiere 3920 will only work on the 2.4 ghz band of your network. This is a single/mono band device. (it cannot see, connect, or use your 5ghz band). Try changing your wireless mode to b/g/n under your 2.4ghz wireless settings as suggested. Instructions below.