Fire TV doesn’t seem to be kodi/4k settable ?

Just picked up a Amazon Fire TV to get 4k Kodi setup and working…. a Samsung UN70KU620DF TV direct via HDMI and I’m not seeing the selections as I do on a PC for setting the playback quality/etc and can’t seem to get anything beyond 1080p with Kodi, though the connection shows 4k/60Hz when the FireTV boots. But the diagnostics info provided by Amazon show the port is HDCP 2.2 compliant, so wonder if anyone can help get Kodi playing 4k files in 4k? When I look at the statistics for video within kodi it shows 1080/24Hz.
Thanks in advance for any help!