to fix this you may need to reset your browsers cache - give that a try and let me know if it helps!
important note:
before you do this, if you still have bitsy game data you want to keep, you should open your browser's JavaScript console from the bitsy page and type in the following code and then press enter:
localStorage["game_data"]
you should see a bunch of text appear in the console - this is the bitsy game data. if you copy it into a text editor (such as Notepad) and save the file with a ".bitsy" extension, you'll be able to reload your game into bitsy after resetting your browser's cache