In Map Viewer Classic, polygon labels will redraw in the best location as you pan and zoom around the map. However, in the new Map Viewer, polygon labels only draw at the polygon centroid. If you pan away from the centroid, the label is out of view and not visible.
It is critical for many applications to be able to see the map label for all visible features in the map extent. It is requested that ESRI , at a minimum, provide the same polygon labelling functionality that existed in Map Viewer Classic. Thanks!