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A: Restart Confluence to resolve it.
2. Q: Why does it fail when “download all attachments”?
A: There are 3 reasons in total:
In "Global Configuration > Attachment Download Restrictions", you have configured restrictions on downloading files with zip suffixes.
In "Global Configuration > Attachment Download Restrictions", you have configured restrictions on downloading files with other suffixes, and the zip file for "download all attachments" exactly contains files with that suffix.
In "More Space Permissions" and "More Page Permissions", you did not grant the user the "download attachments" permission.