1. Be sure to backup all your plugin files and database
2. Download the latest code from Codecanyon here using your purchased account.
3. From WP Admin > Plugins page, delete Super Logos Showcase and Reinstall the latest plugin zip file – superlogoshowcase-wp.zip (Your data and settings will not be deleted)
4. Deactivate and Reactivate Super Logos Showcase plugin at WP Admin > Plugins page
5. Clear cache and refresh the page.
* If there are notices on your WordPress site, go to admin settings page and click on the Save settings button once.
Plugin Auto Update
For auto-update, there’s a plugin called Envato Market that will help you manage and update your purchased Envato Themes and Plugins. You can refer to the references below that might help:
1) http://www.wpexplorer.com/envato-market-plugin-guide/
2) https://www.youtube.com/watch?v=aPm3D78rJDY
* The Envato Market plugin is created and maintained by Envato, for troubleshooting and support, best to contact the plugin author directly.