Hello @kodius11 !
Uhm… that’s a weird problem.
Can you check that the mannequin is in Movable Movility in the Details Panel?
Maybe try creating another one and drop the animation directly to that model.
Or, you can drag and drop an animation direct in the Viewport and that will generate the mesh and the animation added, so you can see if any of those mannequins move when you press play.
I hope any of this helps you!