Error Installing Html Purifier Plugin

I have installed HtmlPurifier and I keep getting this error:

"Please modify the permissions of the cache/ directory in this plugin. The HtmlPurifier plugin needs read/write/execute access to this caching directory in order to avoid a major performance hit."

I have gone into my FTP folder and have tried to change the file permissions to accept all read/write/executable files and I have uninstalled and reinstalled the plugin multiple times.

Please help!

The process of giving access to the "cache" directory should be exactly the same as what you did to give access to the Omeka "archive" directory, both need read, write, and execute access for the server.

The only difference is that, in this case, you obviously need to be working on the "plugins/HtmlPurifier/cache" folder instead of "archive."

I've looked at the access for the cache folder and it says it already has read, write, and executive access for the server. Does it need to match the archive folder exactly? Would that be the problem?