why cannot connect smart card reader on client computer

We develop Website using NFC ACR 122U Smart Card Reader. We have only one problem. When client connect the reader, appear "Connection Fail!" message that message is from code.Please help me! thank

This code is connect card reader.

private void Initialized() { try {

        retCode = ModWinsCard.SCardEstablishContext(ModWinsCard.SCARD_SCOPE_USER, 0, 0, ref hContext);

        retCode = ModWinsCard.SCardConnect(hContext, mReader.ToString(), ModWinsCard.SCARD_SHARE_SHARED,
                                          ModWinsCard.SCARD_PROTOCOL_T0 | ModWinsCard.SCARD_PROTOCOL_T1, ref hCard, ref Protocol);

        if (retCode != ModWinsCard.SCARD_S_SUCCESS)
        {
            lblMessage.Text = "Connection Fail!";
        }

        else
        {
            lblMessage.Text = "Success to Reader.";
            ClearBuffers();

        }
    }
    catch
    {
        if (retCode != ModWinsCard.SCARD_S_SUCCESS)
        {
            lblMessage.Text = "Connection Fail!";
            return;
        }
    }

}