Most common issue is that you don’t have path set to store binary data, directory is missing write permission or the directory is not persistent.
- Go to Settings > System > Database.
- Check if Binary data storage type is set to Filesystem.
- Make sure you have a valid path set for Binary data filesystem path.
- If you are using bind mounts make sure they are persistent volumes.
- Check your directory permissions so that it has write access.
- Restart Stash.
- Go to Settings > Generated Content > Generate.
- Enable Scene covers toggle and run Generate task.