BuddyPress.org

In what sense “but i don’t know what this is”

Have you simply tried selecting one of the other options in the set of available permalink structures, selecting one of these other than ‘default’ causes the system to have to create and write to the .htaccess file.

Can you try – if you haven’t already – selecting another permalink option and clicking ‘save’ and report back what the screen returns as a message.