Hello @Werner Noske. Now that VS Code has replaced Atelier as our cross-platform IDE (Studio is still supported), we have removed the plugin from the Eclipse Marketplace. The page you reference will soon make this clear as well. As @Dmitry Maslennikov says, we encourage developers to follow the guidance in this announcement and move to the VS Code platform if at all possible. Thanks!

This is a very common error. You may be in a rush, or doing too much multi-tasking, then open VS Code expecting to see the IRIS icon signifying your favorite programming extension is ready and waiting. Then to your surprise, it's missing! The likely problem is that you haven't opened a folder yet in VS Code. Just do that and you should see the icon again.