I had to reset my ROKU Express device, my Hisense ROKU TV and my roku premiere because all three were no longer connecting or searching to any of my wireless routers. They stopped about a week after each other and I was devastated. Resetting them didn't work out!! Now I bought the roku stick + and I have clicked OK when prompted about the update after connecting to my wifi and yet the screen just goes blank, I've clicked update just about 13 times now.
With everything dropping off your network like that, i would suspect you have a network configuration or an actual router problem (could be failing) Especially since some of your devices are using your 2.4gz (Express and Premiere) while your RokuTV and Roku Sticks are capable of using both your 2.4gz and 5gz. If network was working even somewhat properly, something should be seeing something,
Reboot your router. Try plugging your Roku Stick power into wall, not your TV USB. Then try setup again.
You may have to access your router's configurations settings. Do you know how? Are other wireless devices connecting to your network ok?
Roku Community Streaming Expert Just another Roku user... I am not a Roku employee. Insignia RokuTV, Ultra 4660, Premiere+ 3921, Express 4k+ 3941, Streambar 9102