Collision between capsule and sphere colliders does not work

I am trying to detect a collision between a capsule collider and a sphere collider with this code but it does not work.

void OnCollisionEnter(Collision other)
	{
		if (other.transform.tag == "fprojectile") 
		{
			Debug.Log("Success");
		}
	}

What’s wrong and how can I fix it?

See the docs for OnCollisionEnter, specifically the part that mentions a non-kinematic rigidbody. You would of course also need the colliding object to have a tag that exactly matches what you have in the script.

P.S. You should ideally use CompareTag instead of using string comparisons.