File not found (page title)
The download URL’s generateMetadata sets the document title to File not found (no period) when getFileForDownloadPage returns null. The page body is usually Next.js’s generic 404, not this exact string.
Why this happens
Bad/typo’d file id in the path, or the file was deleted before the page loaded. API JSON uses File not found. (with a period) in many routes — same idea, different surface.
Diagnose and fix
1. Check the file id in the URL; open the link from My Files / a fresh share.
2. Restore deleted files if that is the case.
3. Distinct from File no longer available (grant existed, file removed later).
4. No Users & limits setting fixes a missing row.