I've tried to upload .AI files to Adobe Stock, but the previews it generates are too dark. They are very, very different from what they should be. I have tried several files with the same result. Yellow becomes orange, for example. And grey areas just go black. That happens to all kinds of files - complex mesh and simple outlines. Any idea why?
Try adding the vector into a zipped folder with a jpeg preview (15MP in size) and upload. That should fix it for you.