Sounds like hactool can't find prod.keys. Fixes:
Ensure you have a prod.keys file:
Obtain prod.keys from your own Switch device (not provided here). Place it in the same folder where you run hactool or specify its path.
Specify the keys file explicitly:
Use the --keys option: hactool --keys /path/to/prod.keys <other options>
Check filename and format:
File must be plain text with lines like titlek=... / prod.keys format expected by hactool. No BOM, correct line endings. hactool prodkeys does not exist
Permissions and path issues:
Confirm hactool can read the file (check permissions). Use absolute path if running from a different working directory.
If using Windows:
Ensure the extension is not hidden (prod.keys.txt). Run terminal in the folder containing prod.keys or give full path.
If you want, tell me your OS and the exact command you ran and I’ll give the exact command to use.