The phpBB SEO Premod includes all the files phpBB 3.0.10 does. Some are of course modified / different than the original files, but none is missing. Download the package again and reupload the files correctly. CHMOD 777 /cache/ + /files/ + /store/ + /images/avatars/upload/.
I install and configure phpBB-SEO (and other mods) for a fair price and very fast. If you are interested simply send me a private message.