I must use
private RigidBody2D rb2d;
I added Rigidbody2D and the script as a component to the player but it doesn’t find it in the script.

,
I must use
private RigidBody2D rb2d;
I added Rigidbody2D and the script as a component to the player but it doesn’t find it in the script.

,
Maybe it doesn’t find the reference because you misspelled it: it’s Rigidbody2D, with the b in lower case.
“B” must be not capital letter
RigidBody2D - fault
Rigidbody2D - true
,“B” must be not capital letter
RigidBody2D - fault
Rigidbody2D - true
Have you opened the C# project/solution created by unity (Either by going to the project directory or by clicking on Assets > C# Project in the Unity editor). If so, Ensure that you have using UnityEngine; At the top of the code.