bbPress.org

I think on the admin panel (bbPress) there’s a link in the description of the permalinks settings part, that when you click it will display the .htaccess code thats meant to be in your .htaccess.

Now I don’t quite know why your having problems but I have also come across problems with something called multi views.

Sometimes permalinks won’t work because of multiviews not being ables. Try adding this to the very top of your .htaccess:

Options +MultiViews