Can't Play Games

I ran into an issue where I am unable to play games in Forge. One moment it was working perfectly, but now it seems to have broken for some reason. When I click "start" to start a game, no new window opens and it only shows the background of my theme. When I exit forge, it shows a message that a game is in progress (which it clearly isn't). I tried downloading the latest version of Forge 1.6.23 but that didn't fix the issue. I have been having this issue for a couple of weeks now. Any idea how to fix it?