I have the same issue with 3.15. Is anyone found resolution to this?
var pointHighlightSymbol = new SimpleFillSymbol(SimpleFillSymbol.STYLE_SOLID, new SimpleLineSymbol(SimpleLineSymbol.STYLE_SOLID, new Color([98,194,204]), 2), new Color([98,94,204,0.8]));
var polyFillSymbol= new SimpleFillSymbol(SimpleFillSymbol.STYLE_SOLID, new SimpleLineSymbol(SimpleLineSymbol.STYLE_SOLID, new Color([255, 0, 0]), 2), new Color([255, 255, 0, 0.25]));
popup = new Popup(
{ fillSymbol: polyFillSymbol, markerSymbol: pointHighlightSymbol },
domConstruct.create("div"));