I just bought a Roku 55 inch 4K. During the setup it allowed me to connect to my Wi-Fi once. As I was in the process of activating my account it stopped working. I restarted the tv and got set back to the beginning of the setup but now it won’t let me connect to my Wi-Fi. It keeps saying theirs no internet even though the Wi-Fi strength is “excellent”. I’ve tried restarting my router, factory resetting, and moving it closer. Nothing works.
Update: I used my phone as a Hotspot to the same Wi-Fi I tried connecting to earlier. And it works. But my tv still can’t connect to the Wi-Fi itself.
There are some router setting issues that can prevent establishing Roku WiFi connections. And to make matters worse, some of them can be set by recently-reported router updates. These have primarily been reported with routers supplied by internet providers (Comcast/Xfinity, Cox, and AT&T so far), but it's possible they could also occur with other internet providers or user-owned routers that have received similar updates.
Your symptoms sound like this one:
Reconfiguring Router
Thanks to forum user @AvsGunnar for providing 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, a restart of the router (even if other devices are still connecting) followed by a restart of the Roku may allow the connection to be reestablished. Depending on your Roku model you'll find the "System restart" option under either "Settings > System > Power" or if you have no "Power" option, under "Settings > System", or if more convenient you can just pull the Roku's power for a few seconds and let it restart.