Why won't Star Wars Battlefront 2 new co op mode work for me?

Hello, I need help I play on Xbox and I've been playing Star Wars Battlefront 2 when it came out. The new Co op mode looks fun but every time I click it (I play on Xbox sorry to remind you again) I press it and my tv goes a little dark then it says "Wait a full minute if this shows up again hold down your Xbox home button for 10 seconds." I unplugged it and tried it some many times but nothing will work. Can someone please help me please?!