Are you able to post a screenshot of what you are seeing? (Upload photo using the little camera/photos icon above near the link/chain icon).
Generally a factory reset is last resort (press and hold the reset button for 30+ seconds or until TV screens enters reset mode), but can try a couple other things first.
See if remote is issue. (Use new batteries or the Roku mobile app available in Play/Apple Stores)
Unplug unit for 10-15 min. (Normally a couple of mins is long enough, but 10-15 is recommended to dissipate any heat related issues).
If TV won't boot to the main Home screen or last used Input, normally not a good sign and factory reset is probably your best shot. (Assuming here you have a Onn RokuTV and not a Onn TV with a Roku device attached.)
Roku Community Streaming Expert
Just another Roku user... I am not a Roku employee.
Insignia RokuTV, Ultra 4660x, Premiere+ 3921, Express 4k+ 3941