I’ve been wrestling with an issue for what seems like ages: every time I try to change the permalink structure on a particular WordPress website everything explodes and every page I try to navigate to gives me a 403 Permission Denied error. Yikes!
Finally found the solution and luckily it was a simple fix: just add the following line to the very top of your htaccess file:
Options +ExecCGI +FollowSymLinks -Indexes -MultiViews
Success! Now the permalink structure can be changed to whatever I want and everything continues to navigate perfectly.