In general your progress in games is stored in local storage (or cookies) in your browser. If you have a browser setting that deletes your cookies every day or session, then also your local storage is cleared and your progress is destroyed. To keep your progress in such situations, you need to add our site to sites that are allowed to have cookies: so add htmlgames.com to your allowed list (since there are our games hosted).
Also playing in incognito mode will not work for keeping your progress.