Samsung 8000 Series User Manual page 554

Check whether Anynet+ (HDMI-CEC) is set
to On in the Anynet+ setup menu.
Check whether the TV remote control is in
TV mode.
Check whether the remote control is
Anynet+ compatible.
Anynet+ doesn't work in certain situations.
(Searching channels, operating Smart Hub or
Setup, etc.)
If you have removed and then reconnected
the HDMI cable, please make sure to search
devices again or turn your TV off and on
again.