More details: https://stackoverflow.com/questions/31553376/eclipse-how-to-install-a-plugin-manually
Uninstall the Snyk Plugin from the Eclipse Marketplace
Help > Eclipse Marketplace > Navigate to the Installed tab to find Snyk Vuln scanner
Click Uninstall for the Snyk Plugin that you have installed, if applicable
Accept any changes and click Finish
Restart your IDE
Download the Beta version of the Eclipse Plugin from Github
Click on Releases and select the version of the plugin that you wish to install
Unzip the file to a folder on your system
Install the plugin in Eclipse
Help > Install New Software...
Click Add, Select Local and browse to the downloaded Zip file
Check the box next to the Snyk Vuln Scanner and click on Next
Click Next, review any prompts and continue.
Once Completed, it should prompt you to restart your IDE once more.