I tried a new approach based on another posting I found - see below.  This works great - instantaneous response however, if I run this code a second time, the call to ConnectionBuilder.Build hangs up and never returns. 

    Private Sub btnGetPrinterStatus2_Click(sender As Object, e As EventArgs) Handles btnGetPrinterStatus2.Click
        Dim connection As DriverPrinterConnection = Nothing
        Dim byteArray As Byte()
        Dim result As List(Of String)

        Try
            connection = ConnectionBuilder.Build(_currentUsbPrinterName)    *** Hangs up if I run this code again
            connection.Open()
            Dim getstatus As String = "~HQES"
            byteArray = Encoding.ASCII.GetBytes(getstatus)
            Dim response As Byte() = New Byte(149) {}
            connection.Write(byteArray)
            connection.WaitForData(3000)
            response = connection.Read()
            result = ParseResponse(response)
            If result.Count > 0 Then
                lblMessage.Text = result.Item(0)
            Else
                lblMessage.Text = "No result returned."
            End If
        Catch ex As Exception
            MsgBox(ex.Message)
        Finally
            If connection IsNot Nothing Then
                connection.Close()
                connection.Dispose()
            End If
        End Try

    End Sub

Hi Steven, We don't think we're aware of this issue, so can you share some details? 
What OS?  Driver (version?) or direct USB? What platform (Android/Windows Java/Windows C#/etc.)?  What version of the library? What firmware version?

Thanks,
Robin

Hi Robin,

I'm facing the same issue; we have several dozens of (old) GK420 printers, this usaually takes about 1 or 2 second, but on the (new) ZD420, it takes more than 10 seconds; on a mac is takes about 1 or 2 seconds.

Please advise since printing during waiting for the status reply is not possible; this causes huge deplay for large volume printing.