Channel verified but i can't upload custom thumbnails

[OpiumSymposium]

maybe there are some kind of requirements like have 2-3 videos uploaded with some views & few subs & after a week you get these options

That could be the case although it isn't stated anywhere. So... no idea.

 

[PainfullyAware73]

I had the same problem. When you upload a video click on "upload with classic" on the upper right hand of the upload screen. Then click on "go to legacy uploader" on the bottom of the screen.. Now when you upload a video from the "classic" the custom thumbnail option will work.