File Not Found

I'm running a site with around 25 files for download. Existing products work fine. Added a new file for download but Drupal doesn't see the file in the directory.

I can see the file in both SSH and SFTP so I know it's there and in the right dir.

I've run cron, flushed all caches and even restarted MySQL.

No matter what the correct file doesn't appear as an option under "reference existing" "Add a new file" field at /admin/commerce/products/*/edit, although I can see all the other, older files.

I'm stumped.