I will try to understand you. You can't play this game "online"? I think you mean you play it in a browser, also because of the blackscreen bug? Perhaps it looks like online, but your browser downloads the game data to your computer and start the game also there. Savegame data in browsergames are mostly stored in cookies. The Cookies are also stored local on your computer. Each browser stores his cookies on there own way, so you can't access a cookies from another browser. The update you mean to play is not really an update. It´s the next standalone version of the game. So now you have your old cookies with all your savedata from your playtime with the older version and the new version with a new separate cookie at this point mostly empty, because you didn`t played and saved here.
You can try to find your old cookiedata in your browser. It´s in options and there in security. But if you wanna look deeper in cookies, you need special programms. Google for "browse cookies" or "edit cookies".
Anyway i need about 4 hours playing this game new from start to end. You can also switch to a non-browser version of this game. If you are not playing on android you have no problems with your savedata then.
So you have 3 options. Replay the game. Replay a non-browser version. Try to restore your cookiedata.