If URL rewriting is not working on your server, site will not function at all. While you might be able to navigate around, all pages will result in HTTP Error 404 or 403. URL rewriting (or "pretty urls") might be not working because of several things:
.htaccess file from CodeCanyon zip did not get copied over properly to your server.
Apache mod_rewrite module is disabled on your server, you will most likely need to contact your hosting support regarding this, unless you have access to server configuration.
Overrides via .htaccess file are not allowed, you will most likely need to contact your hosting support for this as well.
You are using nginx or windows server instead of apache. You can find nginx rules here, and windows server has a module that allows you to import .htaccess file or there are several online services that can convert .htaccess file to web.config