There are some router setting issues that can prevent establishing Roku wifi connections. And to make matters worse, some of them can be caused by recently-reported router updates. These have primarily been reported with routers supplied by internet providers (Comcast/xfinity, Cox, and ATT so far), but it's possible they could also occur with other internet providers or user-owned routers that have received similar updates.
ROKU LOCATES NETWORK AND REPORTS NETWORK QUALITY BUT CANNOT CONNECT Some router updates have changed the router's connection settings on the 2.4 GHz wifi band from b/g/n to just g/n, causing Rokus connecting to the 2.4 GHz wifi band to lose their ability to connect to the network. The solution is to set the router's configuration back to using b/g/n.
Forum user @AvsGunnar has provided the links below to instructions for reconfiguring router settings for the listed internet suppliers. If you can't do this yourself, you may need to contact your internet provider to make these changes for you:
If your problem was not caused by any of the above, often a restart of the router (even if other devices are still connecting) followed by a restart of the Roku will allow the connection to be reestablished. Depending on your Roku model and Roku version number you'll find the "System restart" option under either "Settings > System > Power" or "Settings > System", or if more convenient you can just remove the Roku's power for a few seconds and let it restart.
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