You didn't tell us what model Roku you have, and it might make a difference. But let's assume it's using the 2.4GHz radio band. It sounds like you are seeing your WiFi, so it's likely using a channel that Roku supports. Who is your Internet service provider? Do you rent/lease the router/modem from them? If your ISP has control of your router/modem, they have likely made a change to a setting that is causing the problem. This setting is usually labeled as "mode". There are a number of possible settings for the mode. Chances are your ISP has changed it to "G/N". In theory that shouldn't be a problem for Roku devices, but for some unknown reason it does. You need to change the mode to "B/G/N", and then your Roku should connect. If by chance the ISP also changed the channel width to something other than 20 MHz, it should be changed back.
We don't know why some ISPs have changed these settings on customer's equipment, but that has usually been what has happened, and changing that setting back should resolve your issue. If you can't change the setting yourself (some ISPs lock the user out of some settings) you will need to contact their tech support to make the change.
Dan
Roku Community Streaming Expert
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