WinSCP .NET assembly error: Unable to find type [WinSCP.EnumerationOptions]

Getting this error when loading WinSCP .NET assembly.

Error: Unable to find type [WinSCP.EnumerationOptions]: make sure that the assembly containing this type is loaded.

Windows Server 2008. WinSCPnet.dll dated 25th ‎June ‎2014 1.1.6

Script

param (
    $remotePath = "/Temp/AAA/BBBB/",
    $wildcard = "*.BAK"
     )

try
{
    # Load WinSCP .NET assembly
    Add-Type -Path "D:\XXX\XXX\WinSCPnet.dll"

    #Add-type -assemblyName "System.ServiceProcess"   

    # Setup session options
    $sessionOptions = New-Object WinSCP.SessionOptions -Property @{
        Protocol = [WinSCP.Protocol]::Sftp
        HostName = "AAAA"
        UserName = "BBBB"
        Password = "CCCC"
    }

    $session = New-Object WinSCP.Session

    try
    {
        # Connect
        $session.Open($sessionOptions)


        # Get list of matching files in the directory
        $files =
            $session.EnumerateRemoteFiles(
                $remotePath, $wildcard, [WinSCP.EnumerationOptions]::None)

        # Any file matched?
        if ($files.Count -gt 0)
        {
            foreach ($fileInfo in $files)
            {
                Write-Host ("$($fileInfo.Name) with size $($fileInfo.Length), " +
                    "permissions $($fileInfo.FilePermissions) and " +
                    "last modification at $($fileInfo.LastWriteTime)")
            }
        }
        else
        {
            Write-Host "No files matching $wildcard found"
        }
    }
    finally
    {
        # Disconnect, clean up
        $session.Dispose()
    }

    exit 0
}
catch
{
    Write-Host "Error: $($_.Exception.Message)"
    exit 1
}