Joel,
That should work. Sounds like a bug.
You can manually transfer the files. In your Photo Mechanic preferences folder (for me this is in C:\Users\kbaker\AppData\Roaming\Camera Bits, Inc\Photo Mechanic) there is the 'fileupload' folder. If you want to copy everything and replace all of the Uploader settings on the older Windows 8.1 laptop then copy this folder and its subfolders over to that computer. Otherwise, if you only want the FTP connection settings, open the fileupload folder then open the templates folder and then the builtin folder inside it. You'll see a file named FTP-conn.yml which you can copy to the same place on your laptop and all of the FTP connection settings will be replaced.
HTH,
-Kirk