I'm playing single player, after I go through the medical area and am out in the streets. You're supposed to find the subway entrance. I go through the store and jump up on the roof in the alley and I can't move. I can move my head around, I can aim but I can't activate any skills. It tells me to press D to activate armour mode but nothing happens. I've tried this countless times with the exact same result. Talk about a game breaker.