Try navigating to Settings...System...System Update [Press OK]
Then do a System Restart. Settings...System...System Restart.
If this does not resolve issue, something may have gone wrong during the Setup Process. You may have to perform a Factory Reset and set up the unit again. Settings...System...Advanced System Settings...Factory Reset.
Final thing I would check is that you are using the supplied power plugged directly into the wall outlet, not to the back of your TV power port. An underpowered device will not perform properly. If this is not your issue, I think the factory reset is your best shot.
Feel free to post an update or if you need more help.
Roku Community Streaming Expert
Just another Roku user... I am not a Roku employee.
Insignia RokuTV, Ultra 4660x, Premiere+ 3921, Express 4k+ 3941