Objects not spawning when I play the game on a Phone

I have a problem. When I build my game to android and deploy it to a device, some objects don’t spawn at all.

The game basically spawns boxes and moves them towards the player and the player has to avoid them. The boxes don’t spawn on phones, but it does when I test it on my computer. I have no idea what is going on. Below is my spawning script. It used to work before, I don’t what happened.

public class Randomize : MonoBehaviour {

	// --- Variable Declaration --- //
	public GameObject Prefab;
	public float objectsPerSecond = 5;
	public float MaxDistance = 5.0f;
	public float spawnTimer = 5; 

	// Spawn Objects
	private void spawn()
		// loop based on how many objects to spawn per second
		for(int i = 0; i < objectsPerSecond; i++)
            // Y axis
            float height = Random.Range(-4.0f, 4.0f);
            // X axis
            float distance = Random.Range(0, MaxDistance);
            // clone the objects
            // move the objects
            Prefab.transform.position = new Vector2(10 + distance, height);

	void Start()
		// call the spawn method to spawn the boxes.
		InvokeRepeating ("spawn", spawnTimer, spawnTimer);

I got it.

Basically my boxes were not moving because their speed was being set to 0 at the start of the game after I added a difficulty slider. So I set the ‘starting value’ to a reasonable value.