How do I fix two FirstPersonController prefabs clashing together?

Hi,

So I'm a first year Game Dev Student, and our assignment is to make a Puzzle Coop Game, which is meant to be played with multiple players on a single computer. So. Naturally I need 2 cameras. And 2 FirstPersonController prefabs, one for each player.

However, with both controllers in place, while controlling the first one, I can only move the camera with my mouse on the X-axis and not on the Y-axis, the camera refuses to go up and down. While with the second FirstPersonController disabled, the first one works fine. So, naturally, they're clashing.

Anyone have any clue what I mean and how to fix it? Thanks in Advance

--David