1080p is missing from Youtube App

i am using android 4.4.2 which came preloaded on Android TV BOX, it is capable of playing 1080p videos on it , and ican see them on my big TV too which is also 1080p TV,

But when i use Youtube App from Google in Android TV Box , there is no 1080p option to play the youtube videos in 1080p the max option there is 720p,

How can i get 1080p option in youtube app ?

My box i set to 1080p 60 Hz, Tv is set to 1080p 16:9

i have tried other moethods i found on internet like,

Reinstalling youtube app, cleaning app data, rebooting various time, changing prop value to 4.4.2 android which already is 4.4.2

but still no luck, so how can i view youtube videos in 1080p ?