Can't switch target on train, using mouse and keyboard

i get to the part where it teaches you switching targets while on the train with storm troopers, using a mouse it says to click scroll wheel to target one of the enemies. I do that and i target the first enemy to the left. The game then prompts me to flick my mouse to the right to swap targets, it doesn't work. I've tried restarting and also changing the target lock key-bind, but i don't have the option to change the key-bind for swapping between targets Nothing seems to work.