I created an organization map using AGOL. It has the thumbnail automatically created for it. I go to the details page, click on edit, and then on the thumbnail picture to change it. It states the size should be 200 by 133 for best results with other sizes adjusted to fit. The formats are png, gif, and jpeg. My image is 200 by 127 pixels in jpg format. I also tried JPEG for an extension type. It will navigate to and find my image, but it doesn't seen to upload it because when you click OK, you get a circle with a slash through it. What is the correct procedure to change a thumbnail?