Roku models Express, Express+, Premiere, and Premiere+ are lower end models that have single-band wifi that only connects to the 2.4 GHz wifi band. They cannot connect to the 5 GHz wifi band and don't even see it. If you have one of these models and a dual band router with both 2.4 and 5 GHz bands, be sure the router's 2.4 GHz band is turned on.
There have been a number of reports lately of people that have routers supplied by their Internet Provider having their router's 2.4 GHz band disabled. They've had to have their Internet Provider re-enable the 2.4 GHz band, or even swap in a new router.
Another thing to check is which channel in the 2.4 GHz band your router is set to use. Rokus only support channels 1 through 11 that are used in the US. Some other countries also use a few 2.4 GHz bands above 11, but the Roku can't use them.
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