I'm also on Firefox and having the same issue. I deleted the website's cookies, and the game can run again. But the save data will be gone if you didn't back it up.
Ape Apps, LLC is an independent software development company founded in 2010 by Brandon Stecklein. Over the years, Ape Apps has published over 400 apps and games across various platforms. You can get in touch with Brandon on Twitter or by leaving a post on his wall @bastecklein