I have been running into this issue as well with my parcel layer on AGOL, but I noticed something today. My parcel layer was uploaded from ArcGIS Desktop as a polygon with a white border and a transparent fill color. Even though the popups would almost never appear when I clicked the center of each polygon feature, they would work every time when I clicked the line (border) of the features. When I went to styles pane for the feature layer and clicked style options and then Symbol Style, I noticed that my current symbol type was a “vector polygon”. Perhaps this is the new default style type when uploading a polygon feature class with a transparent fill color.
If you change the symbol and click the drop down options, you’ll notice two Category types: Classic Symbols & Vector Symbols. I played around with these options a bit and noticed that the vector symbols like “hatch fill”, “landscape”, “pencil landscape” and “polygon fill” all have popups that work when you click the center of the feature.
The only type that doesn’t work is the default type which strangely says that the Current Symbol is “Vector Polygon”, but when you go to the Change Symbol’s Category drop down menu, none of the Vector Symbols are selected. The symbol style that has the check mark beside it is the “Basic Shapes”. The way to fix the style to make the polygons’ pop-us work is the click the grey trapezoid with the black outline underneath the drop-down menu. (See attached screenshot)
I also believe that the reason that the “Map Viewer Classic” works is because there is not an option to change the Symbol style for polygons (i.e. there is most likely only a Classic Symbol style and no Vector Symbol style.) It also should be noted that once you have chosen a different Symbol Style, you can no longer access the default style that has this bug. The closest thing to it is the “Polygon Fill” style under Vector Symbols, but that still allows you to chose a fill color, while the default does not.
