Hi, so when i click grade on a students assignment, it won't allow me to grade and just displays 

"Forbidden

You don't have permission to access /mod/assign/view.php on this server.

Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request."

I have checked permissions for entire folders and sub directory and all are set to 755 so should be accessible, also prior to clicking grade the button looks greyed out anyway:

Image may be NSFW.
Clik here to view.

Thanks in advance