My character won't move on premade terrain

Here is my problem: I've downloaded the Fantasy A.I. asset (here is the link). When I create a scene and I drop those characters on a simple plane created by me, everything works fine, but when I drag them on a premade terrain, the just stand still and do nothing, nor I can move the player. I've tried everything and tried to read all the scripts, but I think I'm missing something more basic, since I'm pretty new to unity. Thank for the answers.