martin wrote:
    Please attach a full session log file showing the problem (using the latest version of WinSCP).
To generate the session log file, set Session.SessionLogPath. Submit the log with your post as an attachment. Note that passwords and passphrases not stored in the log. You may want to remove other data you consider sensitive though, such as host names, IP addresses, account names or file names (unless they are relevant to the problem). If you do not want to post the log publicly, you can mark the attachment as private.    
Here is my code. I am unable to find the log file. 
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        Try
            ' Setup session options
            Dim sessionOptions As New SessionOptions
            With sessionOptions
                .Protocol = Protocol.Sftp
                .HostName = "host"
                .UserName = "user"
                .Password = "pass"
                .PortNumber = 22
                .SshHostKeyFingerprint = "ssh-rsa 2048 d5:e9:b2:29:16:a3:09:fb:e8:6d:67:72:be:88:c8:d6"
            End With
            Using session As New Session
                session.SessionLogPath = "p:\comerica\log.xml"
                ' Connect
                session.Open(sessionOptions)
                ' Upload files
                Dim transferOptions As New TransferOptions
                transferOptions.TransferMode = TransferMode.Ascii
                transferOptions.PreserveTimestamp = False
                Dim transferResult As TransferOperationResult
                transferResult = session.PutFiles("p:\Comerica\DataVault\ACH\TPEPILOCOMOTVSFTP.EFTCLAIMS 09-06-2017 - Copy.txt", "/To_Comerica/TPEPILOCOMOTVSFTP.txt")
                'https://sftp.comerica.com/?token=20079AB7-94AE-11e7-80E2-42F2E966EE8F#/To_Comerica/
                ' Throw on any error
                transferResult.Check()
                ' Print results
                For Each transfer In transferResult.Transfers
                    Debug.Print("Upload of {0} succeeded", transfer.FileName)
                Next
            End Using
            'Return 0
        Catch 'e As Exception
            Console.WriteLine("Error: {0}", e)
            'Return 1
        End Try
    End Sub