Also having this issue - multiple games where I'm a player, GM, creator, or combination thereof. When I select "use Charactermancer" on a new sheet, it simply shows me the back-end as if I was editing manually. Confirmed with another user on another browser (I use Chrome, they use Firefox) that they cannot get it to work either. Applet/window does not launch at all. Confirmed no interfering extensions. Windows10, Chrome browser