@Tim Paul I believe the issue you facing is mentioned in this GitHub issue. Try using the relative path like so:
azcopy sync "Y:\Documents\Organisational Change" "https://ocazurenas.blob.core.windows.net/ocazurenas/Organisational Change" --exclude-path="Culture@Recently-Snapshot;Culture\Books@Recently-Snapshot"
Hope this helps. Let me know if you are still facing issues or have further questions.
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