If it stopped creating folders in 2014 something has changed. I would suspect that the access rights of the web service can't create folders any more. Since holidays are always the moment where incisive changes take place, maybe your hosting provider has changed something in this area. Or maybe an FTP file permission slipped unintentionally through your hands
Normally, the folder containing the years subfolders should have chmod 755 or 777, depending on the server settings. If it has become for some reason 644 or similar, the directories are seen, but can't change or extend.