What language is that? VB.NET, VB, VBA?

With old VB/VBA, you cannot use SessionOptions.Timeout. You have to use SessionOptions.TimeoutInMilliseconds. This is available in 5.5.4 and later only.
See https://winscp.net/tracker/1156

I'm trying to override the default timeout value in my SessionOptions code but unable to determine the correct syntax of the timeout setting.

'// setup FTP session options
Dim mySessionOptions As New SessionOptions
With mySessionOptions
.Protocol = Protocol.Sftp
.HostName = FTP.FtpHostName
.UserName = FTP.FtpUserName
.Password = FTP.FtpUserPassword
.GiveUpSecurityAndAcceptAnySshHostKey = True
.Timeout(30)
End With

I've also tried .Timeout = 30 to no avail.