Edit my smm script and clear error

Edit my smm script and clear error

Hello, I have smm script but little issue with it.... my order page telling me this error:
Not Found
The requested URL /index.php was not found on this server. Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.

please tell me if you can check and fix this

Requirements

You should be professional

Skills Required

Mysql Programming Coding Code Coder Php Phpscript Html Html5