Converting from 3D collision to 2D

Hi,

I have a functional prototype of a 2D/side-scrolling game that works using 3D colliders. I need it to utilize only 2D physics components though. This is the first time I've worked with Unity's 2D physics system and I seem to be missing something.
The setup: Each dynamic object in the project has a Box Collider, Rigidbody and Fixed Joint (for manipulation).

The change: I switched these out for Box Collider 2D, Rigidbody 2D, and a Slider Joint.

The problem: All my colliders now immediately fall to the ground, through one another and the boundary collision (they fall through the floor and offscreen). Everything in the project is now using 2D components instead of 3D, and nothing else has changed.

What am I missing?

Thank you!

 

Did you update your code that controls everything? 2D stuff uses all different functions/variables (i.e. Physics2D vs. Physics)

 

Yeap @Senladar is right.
For example:
OnCollisionEnter(Collision) to OnCollisionEnter2D(Collision2D)

So more check Your Physics2DSettings is everything ok. Edit -> Project Settings -> Physics 2D

 

Actually, I think it was the slider joint. In the 3D setup I was freezing the rigidbodies in all axes but the one it was supposed to move in, and using a fixed joint to drag it along that path.
In the 2D implementation I'm unable to freeze the rigidbody translation axes, and because the joint is only active when the user interacts with it, it didnt have anything to keep it in place in the meantime.

Thank you for the replies!