Hi
I guess it's possible that your new computer is using OneDrive by default, and maybe the copy hasn't synced yet, or the very first time you copied it over it corrupted? I would check to see where your Documents folder is, and if there's a copy in OneDrive & a copy on your hard drive, then delete them both and try the copy again. https://support.office.com/en-us/article/Files-save-to-OneDrive-by-default-in-Windows-10-33da0077-770c-4bda-b61e-8c8e8ca70ac7
You might try renaming the folder on the new computer, and copying the entire Games folder in one shot from the old to the new. There could be a file locked or hidden on the old computer that isn't transferring.
If you absolutely can't get it to transfer, you could try creating a new region and transferring each city separately. I've been experimenting with this technique and it works, but it's going to be a long process if it's large region. Step-by-instructions here: How to Transfer Cities Between Regions
I'll give some more thought, if I can come up with any other ideas I will let you know. Please keep us posted - I'm interested in what could be the problem