Build version does not work like the editor one

I've built a 2D platformer for a homework, I just finished it and wanted to build and run it. In the built version jumping on an enemy head doesn't launch me in the air like in the editor and that is what it's supposed to do.

 private void OnCollisionEnter2D(Collision2D other)
     {
         if (other.gameObject.tag == "Enemy")
         {
             if (controller.Falling())
 
 function Falling()
 {
     return m_Rigidbody2D.velocity.y < -0.1f;
 }

That's how I see if I land on an enemy head btw. It works properly in the editor and that is all I want. It kills the enemy when I land on them, but it doesn't launch me into the air.