It's specific to 2.3.1, but you should be able to apply it to your install. Just take a look at the diff here: http://github.com/pkp/ocs/commit/ba329f ... 1dceb1da7d
(if you add ".diff" to the end of that URL, you'll actually get a downloadable unified diff that you can then apply using your server's patch tool.)
Try modifying the files as suggested (keeping backups of your files, of course), and using the plugin again. If that doesn't seem to work, just let us know.