Back Up Documents to One Drive

This error usually means OneDrive detects another important folder inside Documents and will not protect that folder until the nested folder is moved.

Try this end-to-end check:

1. Open Documents in File Explorer.
2. Look for folders named like important Windows folders, especially:
   • Desktop
   • Pictures
   • Music
   • Videos
   • Downloads
   • Screenshots
   • Camera Roll
3. If any of those folders exist inside Documents, move them out of Documents or rename them.
4. Then open OneDrive > Help & Settings > Settings > Sync and backup > Manage backup.
5. Try turning on backup for Documents again.

Also check for these supported causes from OneDrive backup:

• Important folders aren’t in the default locations: OneDrive will block backup if the folder with the error contains another important folder.
• Folder contains a reparse point: if Documents contains a junction point or symbolic link, OneDrive cannot protect it.
• File or subfolder path is too long: shorten the file name or subfolder name.
• A file is larger than 250 GB: remove that file from the folder before retrying.
• Invalid file names: names cannot start with a space or include \ : / * ? < > " |.

If OneDrive moved files into similarly named folders and the original Documents location is now empty, and error 0x80070005 appears, that points to the “Prohibit User from manually redirecting Profile Folders” group policy being enabled. In that case, move the contents back to the original folder location and have the policy changed.

If the issue is only with Documents while other folders back up normally, the most likely fix is removing or renaming any nested folder that matches an important Windows folder name inside Documents.

References:

• Back up your folders with OneDrive | Microsoft Support
• the documents folder contains other important folders and isn't supported for backup - Microsoft Q&A