Well. I can explain that. THIS GOES FOR EVERYONE.
What happens when you import a spray. Is it gets resized to a manageable size so that someone does not import a spray that is the size of 90000x90000 also if the image has an width and height that the software does not know how to resize. sometimes, it cannot resize it. And it will not show up, I belive they might have fixed this but i am not for sure. This is only 1 reason. The other reason, is that it takes time to load the image as the spray. I do not know the reason for it but you must be patient. If you upload the image as your spray now. You should be able to see it either later on in the day or tomorrow. It just depends on how steam is acting lol.