Apple tv remote

That is a function of HDMI CEC.

First verify that you have that turned on in Apple TV (settings - remotes and devices - control TVs and receivers)

Also make sure it is turned on for your TV

Be aware that each manufacturer uses their own implementation (Samsung calls theirs Anynet+) so any issues that arise would need to be fixed by them. You can check if they have any firmware updates, refer to the manual for troubleshooting and contact for support if necessary.

there is a LOT to this answer. are both units (appleTV and samsung TV) allowing hdmi control ?