I can also see your problem now.
The TransferOptions is 7th argument of SynchronizeDirectories. While you pass it as 5th argument.
https://beta.winscp.net/eng/docs/library_session_synchronizedirectories and
https://beta.winscp.net/eng/docs/faq_library_parameters

Many thanks for your reply but I managed to resolve the issue using

$transferOptions.FileMask = "|RESULT*"
$transferResult = $session.GetFiles($remotePath, $localPath, $False, $transferOptions)

instead, as that seems to work with the file mask where as

$transferOptions.FileMask = "|RESULT*"
$synchronizationResult = $session.SynchronizeDirectories([WinSCP.SynchronizationMode]::local, $localPath, $remotePath, $False , $transferOptions)

does not.

Please attach a full session log file showing the problem (using the latest version of WinSCP).

Hi,
this is my first post to the forum so I hope someone can help.

I have a PowerShell script with the following code

$sessionOptions = New-Object WinSCP.SessionOptions
$sessionOptions.Protocol = [WinSCP.Protocol]::ftp
$sessionOptions.HostName = $Remote_Host
$sessionOptions.UserName = $UserName
$sessionOptions.Password = $Password
$Session.SessionLogPath
$session = New-Object WinSCP.Session
$session.Open($sessionOptions)
$transferoptions= New-Object WinSCP.TransferOptions
$transferOptions.FileMask = "*.TXT | RESULT*"

# Synchronize files to local directory, collect results
$synchronizationResult = $session.SynchronizeDirectories([WinSCP.SynchronizationMode]::local, $localPath, $remotePath, $False, $TransferOptions)

It works fine except the file mask does not exclude the RESULT* files in the directory. Am I doing something wrong?

WinSCP version is WinSCP 5.7.5
Windows version is server 2012

Many thanks for any help
Steve