In case you are using softlab24 paid version please contact them for upgrade instructions

Upgrading from any Ossn version to latest one

• Make sure you have at minimum php 7.0 running.
• Back up your complete OSSN site- and data directory.
• Back up your database.
• Download the latest stable OSSN version from the download page of our website and unzip it locally.
• Login to your Ossn admininstrator dashboard - don't log off.
• Disable Cache.
• Upload all files and folders from the locally unzipped archive to the former place on your server via FTP, SCP or a Filemanager of your choice. (When asked to allow overwriting of the old files: Answer YES to all)
• Check the ownership of copied files and folders on your server. They must be read- and writable by the webserver process. In doubt ask your provider how to set permissions correctly.
• Back in your browser, enter YOUR-WEBSITE-URL/upgrade/upgrade.php
• Remove subdirectory named installation

You must follow these steps to upgrade.