Happy to help! I know some people make it work by setting the player to the child of the platform, but I went for a different approach. This is what you should attach to the player. It simply detects if you touch a moving platform, moves you along with it's movement, and detects when you leave the moving platform.
Here's the essentials of the MovingPlatform class (I left out ChooseNewPosition since I'm sure you have your own solution for that). The only part of it you really need to have is "public Vector2 MoveDelta => rb.velocity;" as well as the part where you move it using the platform's rigidbody.
Hope this helps and let me know if you have any questions!
