For the last few weeks I have noticed a problem in Chrome when opening existing web maps. Some layers are "not responding" when loading the map and ultimately "cannot be added to the map." I've cleared the browser cache in Chrome, but it doesn't help.
If I load the web maps in Internet Explorer or Firefox, all layers load fine. Even stranger is that all layers load fine in apps that use the web maps in question when opened in Chrome. So the problem seems to be only when opening the web map in the ArcGIS Online Map Viewer in Chrome.