appletv4 remote won't power off (newer) tv anymore

The tv is a recent Samsung smart tv (UN65KS8000). For the first couple months, the appletv4 would switch on the tv when awoken, and switch off the tv when put to sleep, now this no longer works. HDMI-cec is enabled on both the appletv and samsung television. Another device, a Wii-U, will power on the tv and switch sources when powered on. I have tried another hdmi cable, had both devices check for updates, and powered both down.

Any clues why this would suddenly stop working, and only for the appletv?