I had the same issue and was told it was user error and that pressing the activate button adds a boost regardless of whether you have one already active or not and they stack giving you a massive xp boost instead of just 2xp, that's not true but I complained further and said it is not user error if the games code allows you to activate multiple boosts without telling you they have activated and I was given 3 battlepacks as compensation, it won't replace the 5 boosts I wasted and lets face it I probably wont get any boosts from them but it is better than a kick in the crotch.