This usually means the .htaccess file was not uploaded to your server. See this tutorial for details: Links not working in Sngine
Make the includes folder writable (permissions 777), empty the database (remove any existing tables), then run the installer again. After installation succeeds, restore normal folder permissions.
Nginx and IIS configuration files are included in the zip package under the Extras/Servers folder. For more details, see this tutorial: Sngine on Nginx
Update the config file to use HTTPS. Follow this tutorial for step-by-step instructions: How to run Sngine on HTTPS
