If the file is broken, use a hex editor to check the Start Header and End Header . A healthy 7z file starts with the signature 37 7A BC AF 27 1C .
Identify why the file cannot be opened immediately. Common hurdles for .7z challenges include: The archive requires a key. okayscome.7z
Note: If this command prompts for a password, the archive is encrypted. If the file is broken, use a hex