Error 640 Mac is an error message that shows up when you try to open, extract or access zip files on macOS. It mainly happens when the ZIP file is corrupted, you have an incomplete download or your permissions to the file are incorrect, but also can be when the Archive Utility, the tool you use for decompressing files, is messed up. When Error 640 Mac comes up, you won’t be able to extract the file and So won’t have access to the contents. Sometimes, although rarely, the problem can be due to the archive being in a format that is not supported or the storage media is physically damaged. To fix this error, you can try one or a combination of these: download the file again, verify your permissions, update your macOS version or use a different tool for extracting files.