Go to Notification Panel - Switch Off the "S Pen Air Action" and turn it on again .. The pop up will come select "Connect New S Pen " Then follow the instruction on Screen , pair and use ..
In order to connect your S Pen in your device kindly follow below given steps:-
1. Insert the S Pen into the slot to start the connection >> Open the notification panel by sliding down from the top of the device >> Expand the options in the notification panel >> Slide the notification panel to the left >> Tap S Pen remote >>Tap it again to reactivate it.
If the issue still persist, we request you kindly visit the Samsung service center as your device needs physical inspection.
