Unable to export 4k videos to YouTube
After editing a 4k movie clip in iMovie on iPhone 6s, I'm unable to export it to YouTube in 4k.
The scroll menu includes up to "4k" but after tapping on "share", two overlaying pop ups appear and disappear in a fraction of a second. I think one of the pop up says "unable to upload to YouTube". They disappeared too quickly for me to catch more than a fleeting glimpse every time.
However, if I were to choose 1080, it uploads to YouTube just fine. The edited movie clip is less than 10min.
What can I do to resolve this? I purchased this app just to edit and upload videos to YouTube in 4k. Now it just seems like a waste of both time and money. Is refund possible if there's no solution to this? I call false advertisement in its description.
iPhone 6s, iOS 9.3.1