Re: Dynamics Ax 2009 - The selected file is not a valid .NET assembly
I do not know Dynamics Ax. But based on "2009": Isn't it using .NET framework version older than 4.0?
net40 and netstandard2.0 directory and also the one in the main directory WinSCP-6.1.2-Automation. I've downloaded the said files from here: https://winscp.net/download/WinSCP-6.1.2-Automation.zip/download