Problems converting Session to Class in C #

I have the following variable

List<MyFile> xmlDisponivel = new List<MyFile>();

This variable is a list of the following class

public class MyFile
{
    public string FileName { get; set; }
    public string FilePath { get; set; }
}

In a process I save the list that assigns this variable in a session

Session.Add("XmlDisponivel", xmlDisponivel);

In another process when I try to get this information from the session and pass it to my variable of type List<MyFile> it always comes null even if it has information in the list.

As I print below, I have a list of 400 files, but when I try to convert the session to my variable, it always comes null.

How to solve, any ideas?