[Python] Why does opening file throw PermissionError, but copying and then opening works

I have a file, that is in a cloud (it could be another company computer) and need to open it. When I try to open it via with open(path) as file it throws PermissionError: [Errno 13] Permission denied:.
Copying via shutil.copyfile does not work either.
However when I use os.system("copy ...input, output...") I can copy and open the file.

Can someone tell me, why this is? It works now, but this still bugs me out.

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