cannot read property 'length'

I have looked at other posts on the forum but I don't see the resolution to my issue.

            var ToGenerateTable = $('#ToGenerate').DataTable({
                dom: 'frtip',
                ajax: 'api/ToGenerate',
                dataSrc: 'Table',
                idSrc: 'ImportID',
                columns: [
                    { data: "ImportID" },
                    { data: "DeptName" },
                    { data: "FTE" },
                    { data: "EmployeeCount" }
                ]
            })

json:

{"Table":[{"ImportID":121,"DeptName":"Ag Commissioner","FTE":48.15,"EmployeeCount":50},...