I see this has been asked and sort of answered 3 years ago, but I'm running into it in version 19.2.23. I'm using jQuery 3.4.1 and including the following files via the bundler.  This is the page output for all my includes. No 404 errors on loading any of my pages, so the files are there in the right spot.

  <link href="/Content/Infragistics/css/themes/infragistics/infragistics.theme.css" rel="stylesheet"/> <link href="/Content/Infragistics/css/structure/infragistics.css" rel="stylesheet"/> <link href="/Content/bootstrap.css" rel="stylesheet"/> <link href="/Content/Site.css" rel="stylesheet"/> <script src="/Scripts/modernizr-2.8.3.js"></script> <script src="/Scripts/jquery-3.4.1.js"></script> <script src="/Scripts/jquery-ui-1.12.0.js"></script> <script src="/Scripts/bootstrap.js"></script> <script src="/Scripts/Blob.js"></script> <script src="/Scripts/FileSaver.js"></script> <script src="/Scripts/Infragistics/js/infragistics.loader.js"></script> <script src="/Scripts/Infragistics/js/infragistics.core.js"></script> <script src="/Scripts/Infragistics/js/infragistics.lob.js"></script> <script src="/Scripts/Infragistics/js/infragistics.dv.js"></script> <script src="/Scripts/Infragistics/js/modules/infragistics.util.js"></script> <script src="/Scripts/Infragistics/js/modules/infragistics.ext_core.js"></script> <script src="/Scripts/Infragistics/js/modules/infragistics.ext_collections.js"></script> <script src="/Scripts/Infragistics/js/modules/infragistics.ext_text.js"></script> <script src="/Scripts/Infragistics/js/modules/infragistics.ext_io.js"></script> <script src="/Scripts/Infragistics/js/modules/infragistics.ext_ui.js"></script> <script src="/Scripts/Infragistics/js/modules/infragistics.documents.core_core.js"></script> <script src="/Scripts/Infragistics/js/modules/infragistics.ext_collectionsextended.js"></script> <script src="/Scripts/Infragistics/js/modules/infragistics.excel_core.js"></script> <script src="/Scripts/Infragistics/js/modules/infragistics.ext_threading.js"></script> <script src="/Scripts/Infragistics/js/modules/infragistics.ext_web.js"></script> <script src="/Scripts/Infragistics/js/modules/infragistics.xml.js"></script> <script src="/Scripts/Infragistics/js/modules/infragistics.documents.core_openxml.js"></script> <script src="/Scripts/Infragistics/js/modules/infragistics.excel_serialization_openxml.js"></script>  

Here's the code to set up the click handler for the export button:

        $("#exportButton").click(
            function () {
                $.ig.GridExcelExporter.exportGrid($("#mainGrid"),
                    {
                        fileName: "TmsAutoPayAccruals",
                        gridFeatureOptions: {
                            "sorting": "applied",
                            "filtering": "none",
                            "paging" : "allRows"
                        }
                    });
            });

The button click happens but when it tries to export the grid, I get an undefined type error on $.ig.GridExcelExporter

I know I'm probably missing a JS file somewhere, but I'll be danged if I can find it. I've looked at the examples, the latest being from version 2016.1