The power, volume, and mute buttons control your television directly via infrared (IR) signals, just like your original TV remote.
The rest of the buttons control the Roku functions by WiFi signals directly to the Roku. In order for this to work the remote must be paired to the Roku. If this is a new setup it should have run you through the process initially. If it previously worked and now doesn't, it sounds like it lost its pairing and must be re-paired.
In either case, this article describes the pairing process: https://support.roku.com/article/360011621473
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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Ultra 4800 | Streaming Stick 4K+ 3821 | TCL Roku TV 43S245/C107X
