You might need to create .htaccess file inside your site’s home directory(like : /public_html)
Here is the sample :
# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>
# END WordPress
And also check your files permission. See Details : Here,
Sometime wrong file permissions can creates this issues too.See Details : Here