Try restarting your Roku. From Roku Home Screen, Settings..System..System Restart
Alternatively, you can just unplug the Roku.
If the System Restart doesn't solve issue or issue returns, try using an alternative theme or the default theme pack under Settings...Theme..Theme Packs (select a Roku default)
If the Roku default theme pack solves issue, then most likely culprit was a problem with your selected Theme.
Last suggestion is to make sure you haven't inadvertently toggled some Zoom setting on your TV or your TV remote (not your Roku remote, but your TV remote).
Roku Community Streaming Expert
Just another Roku user... I am not a Roku employee.
Insignia RokuTV, Ultra 4660x, Premiere+ 3921, Express 4k+ 3941