You don't have permission to access /wp-admin/install.php on this server.

Hi.
I want to install wordpress on my shared host. I did it later, and every thing was good; Till someday my admin dashboard missed its styles! And i search and do every solutions, but does not work. So i remove all uploaded files from httpdocs ( panel is plesk and server is linux). and upload wordpress’s files again. But after call my domain name, and fill data, on step 2, its show a error “You don’t have permission to access /wp-admin/install.php on this server.”
Permissions of install.php file was 644. i change it to 755, but does not work; I change it to 777, but does not work again!
I set permissions of all directories to 755, and all files to 644, but error still exist!
I double check web-config.php and everything is OKey.
There is no .htaccess inside of wp-admin, or even root (httpdocs).

Please help me ??