If you have checked and verified that your 2.4ghz band on your router is broadcasting/enabled and configured correctly (channels 1-11, protocol mode g/n or n, and 20mhz channel width), then really the available options for the end user to try before concluding device failure..
1. Restart modem, router, and all access points.
2. Try clearing cache/resetting Roku Network settings. (Settings...System..Advanced System Settings...Network Connection Reset...Reset Connection) After Roku restarts, try pressing SCAN Again a few times when you are in the Network Connection Screen to see if it refreshes.
3. Factory Reset device. (last resort). Either Press the Reset button like you did before for 30+ seconds, or from Roku Menu. (Settings...System..Advanced System Settings...Factory Reset). If failing to see SSID at this point, can try again with your hotspot if an option to you on the 2.4ghz band.
If you normally see other networks in your Network Connection Screen (neighbor's wifi) and those have disappeared as well as yours, a pretty good indicator that either the antenna or wifi chip (both internal hardware) in the Premiere has failed and you will need a replacement device.
Check your account at https://my.roku.com/account, and look at the activation date. If you are under a year, may qualify for warranty replacement. https://support.roku.com/article/208757058
Since the Premiere models have currently been discontinued, the logical replacement would be the new Express 4k models or upgrade to the Ultra. The new Roku devices are all now capable of both 2.4 ghz and 5 ghz capability if you need wireless connectivity. Also now have ethernet capability (built-in or adapter) which can potentially extend the usable life of the model if/when internal wireless hardware fails.
Post back with any updates or if you need more help.
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
