Smart Slider 3 is activated, but it doesn't show up in the WordPress admin menu

Error
  • Smart Slider 3 was installed and activated in the Plugins list, but it doesn't show up in the WordPress admin menu
  • Destination folder already exists. /wp-content/plugins/nextend-smart-slider3-pro/ Plugin installation failed.
Solution
This kind of problem can happen when a server is misconfigured and by installing our plugin the folders and files weren't created with the correct permissions and you don't have access to see them. You should rather follow the  FTP installation method, because that usually creates folders and files with the correct permissions and hopefully that will work for you too! You can just overwrite those files you already have in your plugins folder.
If this wouldn't work either, another problem could be if your server has cache. If a server cache isn't cleared, the new PHP files aren't running, so if you know about a server cache on your website, you should clear it. If you aren't sure or that wouldn't work either, you should contact your server host and ask them to fix the permissions of the folders and files, so you would be able to access them from your admin area.