I don't really know what you mean that you use "just google. Not google chrome" Google is a company and a search engine, there are two browsers Chrome and Chromium, there's also a default browser on Google telephones, maybe you mean that?
In the menu if you press on the little arrow next to the tree link you will have an option whether to open up Flash or HTML5. But keep in mind that if your browser does not load flash within seconds, then Geni will just redirect you to HTML5 regardless of your choice.
Flash is blocked because you have not unblocked it... Where to unlock depends on which browser you are using. On Chrome (https://www.google.com/chrome/) you just click on the padlock 🔒 the URL field to unlock
You might have to install latest version first https://admdownload.adobe.com/bin/live/flashplayer32pp_xa_install.exe
Keep in mind that Flash is slowly dying. Most companies are no longer supporting it. And Geni absolutely correctly develops only its HTML5 version from now on, unfortunately it is far from useful for not, it kind of feels like something that was thrown together so that it kind of allows a person to do what they want.
So even if you make it work, it is only a matter of time before it breaks again.