It is your browser security/privacy settings that is causing the issue. Brave and incognito simply will not perserve the data that has your saves/settings. Others also wont depending on your browser settings.
Sometimes when an update happens the url et cetera that itch is hosting from for the game (which is running in an iframe) changes, People have definitely had that trigger the privacy stuff before when it wasn't.
Unfortunately there just isn't a fix outside of trying different browser or getting the proper whitelist setup et cetera.