Unity 2d collider not working?

Question

Unity

I make my first platformer (2d) immediately an error, went in, added graphics (one character and platform) added RigidBody2d and boxcollider2d to the character and boxcolider2d to the platform, launched, the player fell through the platform, before that I made a 3d game (the first game in my life ) everything works fine and colliders and physics, I also note that I’m making the game on android, and the engine chose 2D mobile core made the menu on a separate stage, pressing the button loads the game menu!
Tell me what could be the problem?

Answer 1

0) everything happens in the wrong plane
1) the collider is in trigger mode
2) there are no collisions between layers (to which objects belong) ( https://docs.unity3d.com/Manual/LayerBasedCollisio... )