I've posted video to Instagram but the post appears black...

[defaultorwpk8pzk1zs]

The video is working fine, it just shows a black video when posting or sending to someone. How do I make the first screen the "saved" screen. It's the one in the upper left corner

[Trevor288406424zrt]

Hi there, have you used any transition effect at the start of the video? If yes, you need to remove it as I have the same problem before but not any more after I keep the start simple and effect-free.
You can also upload a separate 'cover image' for your reels/videos in IG which will overwrite the start of your video to be the thumbnail pic on IG.