The AddFromFile Action invokes a OpenFileDialog dialog to obtain a file name to be added (multiple files can also be selected). For each selected file, a new object is created and its IFileData type property is initialized with the selected file. The IFileData property that stores a file is specified via the FileAttachmentAttribute applied to the current persistent object declaration.
To ascertain why the AddFromFile Action is currently deactivated or disabled, use the DiagnosticInfo Action. If you need to change the Action's "active" or "enabled" state in code, use its ActionBase.Active or ActionBase.Enabled property, respectively.