What this error means
XDM downloads into a temporary folder and, once everything has arrived, moves the finished file to the download folder (or the folder of the matching category). If that last step fails, you see this error. The downloaded data is kept: after you fix the cause, Resume only finishes the move. Nothing is downloaded again.
Fix it
- Check the destination exists and is writable. If it's on an external or network drive, make sure it's connected. Pick another folder if you're not allowed to write there.
- Free space on the destination drive. When the destination is on a different drive than the temporary folder, the file is copied, so it needs the full file size free.
- Close programs using a file with the same name. A media player or the antivirus scanning an older copy can lock it. Or turn on Overwrite existing files in Settings → General.
- Check the file name. Very long names or characters your file system doesn't accept can fail. Right-click → Properties to see it.
- Allow folder access. On Windows, “Controlled folder access” (ransomware protection) can block apps from writing to Documents, Pictures or Desktop. Allow XDM there. On macOS, allow XDM in System Settings → Privacy & Security → Files and Folders.
- Click Resume. XDM retries the move.