If the Roku responds to the remote, try returning to the Home page and restarting the unit via Settings > System > System restart.
If it is locked up to where it won't respond to the remote, restart by disconnecting the power then reconnecting after 30 seconds or so.
Roku Community Streaming Expert
I am not a Roku employee, only a user like you. Please, no support questions via private message -- post them publicly to the Community where others may benefit as well.
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Streaming Stick 4K+ 3821 | Streaming Stick+ 3810 | TCL Roku TV 43S245/C107X