Forbidden error come while grading the assignement

Hello Friends,

I have frequently getting 404 error while giving grade to the student. But I can prevent submission change or give grant extension. (My moodle version is 2.4.1)

I didn't understand.

error details which I got.

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.

Can any one provide solution on this issue.

Thanks for help in advance.