No guarantees, but this has always worked for me when I've needed to re-establish the WiFi connection on a Roku device. Try this, in this order:
Reboot your router (Yes, do this even if your other devices have no problem finding and connecting to your network.)
When your router comes back up, restart your Roku via:
Separate Roku device: Settings > System > System restart
Roku TV: Settings > System > Power > System restart
Reconnect to your network via Settings > Network > Set up connection
If this still doesn't work, try pulling the power plug on your Roku for a minute or so then plugging it back in. When it's finished restarting, try to reconnect the network again.
Roku Community Streaming Expert
I am not a Roku employee, only a user like you.
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