I received error message (4000). It is not on the list of possible error messages.
What to do about an error (4000)?
Windows, Windows 6
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See this discussion about iOS14 Error 4000 --> https://discussions.apple.com/thread/251804526
which was recommended by an Apple Community Specialist in this post --> https://discussions.apple.com/thread/252380437?answerId=254515885022#254515885022
Another solution by manually selecting the update file in WIndows:
https://discussions.apple.com/thread/252708257?answerId=255119643022#255119643022