These things are just special purpose computers, and just like their big brothers, sometimes operational problems cans be solved by a system restart.
From the Roku home screen use menu path Settings > System > System restart. (On a Roku TV the menu path is Settings > System > Power > System restart.)
If you prefer, or if the problem you're having doesn't let you control the Roku via the remote, you can restart by pulling the power plug for 30 seconds or so then plugging back in.
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.
If this post solves your problem please help others find this answer by clicking "Accept as Solution.".
Streaming Stick 4K+ 3821 | Streaming Stick+ 3810 | TCL Roku TV 43S245/C107X