My collectible/score script isn't working. Anyone have any idea why?

My collectible/score script isn’t working. It should add 1 to score every time player collides with something with the tag “collectible”. Right now it just gives this message when colliding with a collectible. The error is this: NullReferenceException: Object reference not set to an instance of an object score.OnTriggerEnter (UnityEngine.Collider col) (at Assets/Scripts/score.cs:27)
Anyone have any idea why?
Here is the code of my score script:

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;
public class score : MonoBehaviour {
    public float Score = 0;
    public float previous = 0;
    public Text sscore;
    public float emptyValue = 0;
    // Start is called before the first frame update
    void Start()


    // Update is called once per frame
    void FixedUpdate()

    void OnTriggerEnter(Collider col)
        if (col.gameObject.tag == "collect")
            Score = previous + 1;
            previous = Score;
            sscore.text = Score.ToString();

If someone finds a fix, thank you!
Oh, and this is a 3d project.

click in the object that script is attached too, and make sure the sscore var is assigned, 90% sure thats the error.