I had a stubborn pairing problem one time that was solved by pairing the previously-paired remote as a new device.
Settings > Remotes and devices > (+) Add devices > [√] Remotes
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.".
Ultra 4800 | Streaming Stick 4K+ 3821 | TCL Roku TV 43S245/C107X