I believe this question was asked before but I cannot find it in this community: Is selected feature in map image not highlighted in New Map Viewer? Here is an example where you can click on any road to open the pop-up, but the selected road is not highlighted.
This is currently not implemented on map image layers and image layers but is on our roadmap in the JSAPI and then Map Viewer and other 4.x apps will get this highlight support.
