Hi nauna,

The path of the excel file is mapped to OleDb using Server.MapPath method.

Since you are using online path as excel use below article and pass the stream.

Read Excel file directly from Stream in ASP.Net

Check this example. Now please take its reference and correct your code.

HTML

<asp:Button ID="btnImport" runat="server" Text="Import" OnClick="ImportExcel" />
<hr />
<asp:GridView ID="GridView1" runat="server">
</asp:GridView>

Namespaces

C#

using System.IO;
using System.Data;
using System.Net;
using ClosedXML.Excel;

VB.Net

Imports System.Data
Imports System.IO
Imports System.Net
Imports ClosedXML.Excel

Code

C#

protected void ImportExcel(object sender, EventArgs e)
{
    string url = "https://file-examples-com.github.io/uploads/2017/02/file_example_XLSX_10.xlsx";
    using (XLWorkbook workBook = new XLWorkbook(GetStreamFromUrl(url)))
    {
        IXLWorksheet workSheet = workBook.Worksheet(1);
        DataTable dt = new DataTable();
        bool firstRow = true;
        foreach (IXLRow row in workSheet.Rows())
        {
            if (firstRow)
            {
                foreach (IXLCell cell in row.Cells())
                {
                    dt.Columns.Add(cell.Value.ToString());
                }
                firstRow = false;
            }
            else
            {
                dt.Rows.Add();
                int i = 0;
                foreach (IXLCell cell in row.Cells())
                {
                    dt.Rows[dt.Rows.Count - 1][i] = cell.Value.ToString();
                    i++;
                }
            }
        }

        GridView1.DataSource = dt;
        GridView1.DataBind();
    }
}

private Stream GetStreamFromUrl(string url)
{
    byte[] bytes = null;
    ServicePointManager.Expect100Continue = true;
    ServicePointManager.SecurityProtocol = (SecurityProtocolType)3072;
    using (WebClient wc = new WebClient())
    {
        bytes = wc.DownloadData(url);
    }

    return new MemoryStream(bytes);
}

VB.Net

Protected Sub ImportExcel(sender As Object, e As EventArgs)
    Dim url As String = "https://file-examples-com.github.io/uploads/2017/02/file_example_XLSX_10.xlsx"
    Using workBook As New XLWorkbook(GetStreamFromUrl(url))
        Dim workSheet As IXLWorksheet = workBook.Worksheet(1)
        Dim dt As New DataTable()
        Dim firstRow As Boolean = True
        For Each row As IXLRow In workSheet.Rows()
            If firstRow Then
                For Each cell As IXLCell In row.Cells()
                    dt.Columns.Add(cell.Value.ToString())
                Next
                firstRow = False
            Else
                dt.Rows.Add()
                Dim i As Integer = 0
                For Each cell As IXLCell In row.Cells()
                    dt.Rows(dt.Rows.Count - 1)(i) = cell.Value.ToString()
                    i += 1
                Next
            End If
        Next

        GridView1.DataSource = dt
        GridView1.DataBind()
    End Using
End Sub

Private Function GetStreamFromUrl(url As String) As Stream
    Dim bytes As Byte() = Nothing
    ServicePointManager.Expect100Continue = True
    ServicePointManager.SecurityProtocol = CType(3072, SecurityProtocolType)
    Using wc As New WebClient()
        bytes = wc.DownloadData(url)
    End Using

    Return New MemoryStream(bytes)
End Function

Screenshot