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

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Requirements

You should be professional

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Skills Required

Mysql Programming Coding Code Coder Php Phpscript Html Html5