In general your progress in games is stored (automatically) in local storage (or cookies) in your browser. If you delete your cookies or 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 avoid this issue please allow cookies, but if you do not want to do that for all sites: add the site where our games are hosted to sites that are allowed to have cookies. So add htmlgames.com to your allowed list.
Also playing in incognito mode will not work for keeping your progress. And make sure you allow cookies to be stored.