I’m having the same problem on multiple Roku Premier devices starting about two days ago. So are multiple others in these forums. Have been through all the troubleshooting to no avail. Other wifi devices working fine. Speed and signal strength not a problem. Shows my network on list but will not connect.
What network frequency is your router using? If you have the Roku Premiere and it is a single-band wireless device which means it only supports a 2.4 GHz connection. Your Roku Premiere will not recognize the 5Ghz network. You need to make sure that your 2.4 GHz network is active by using your mobile phone and check if you can detect the 2.4 GHz network. We also suggest you reach out to your Internet Service Provider or ISP for assistance in checking if the 2.4 GHz network is active and not hidden.