I'm pretty sure this has been discussed before but the solution I read then doesn't seem to work now. I have a layer in ArcGIS Online that I have symbolized using an image/icon found elsewhere online. When I symbolize the layer I simply select "Use An Image", and paste the path to that image, select OK, OK, Done, and then save my changes. I can view the layer with that symbology at that point; however, after I log off, and then log back in the changes are not saved. I cannot seem to save this symbol for this layer, regardless of how many times I select "SAVE".
In the past one solution was to copy the icon/symbol image to the ArcGIS Online server/cloud, in the same folder as where the map that contains that one layer resides. At first this seemed to work, but now it longer does. This is particularly frustrating because we are trying to demonstrate the GIS capabilities to many users in our office and the last two demos have failed because the symbology just does not draw (and it's an important layer for our business too).