Thanks to all. The data are shapefiles created from land surveyed points that are three-dimensional. I succeeded with a test map by following Jayanta's suggestion. In ArcMap, when I loaded the points from Excel and used the command Display XY data, I left the Z field as none. (I had been specifying that field with the actual elev data). When creating a shape file from the points, I can still have the elev data in the attribute table. The test map with just this point file did work in Explorer. HOWEVER, this app is a bummer. Not as good as the old one, ESRI ArcGIS app. Not as easy to click on the features. No magnifying glass when you press your finger (as far as I can tell.) Hopefully, this app will be improved. The old app still works, but iPhone reports it needs updating, and it no longer appears in the app store.