Resolution is not saving.

I am having a problem with the resolution. The resolution is not saved. When I close the game and reopen it at first it opens fine and suddenly it changes to a default resolution and I have to change it again. I do not understand what is wrong in the code that the resolution is not saved. I already tried a thousand ways and I can’t solve it. Here is the code that I am using to change the resolution and save it:

public class LogicResolution : MonoBehaviour
{
    public TMP_Dropdown resolutionsDropDown;
    public int optionIndex;
 
    void Start()
    {
        optionIndex = PlayerPrefs.GetInt("resolutionNumber", 2);
        resolutionsDropDown.value = optionIndex;
        AdjustResolution();    
    }
 
    public void AdjustResolution()
    {          
        if (resolutionsDropDown.value == 0)
            Screen.SetResolution(640, 360, Screen.fullScreen);
        else if (resolutionsDropDown.value == 1)
            Screen.SetResolution(1280, 720, Screen.fullScreen);
        else if (resolutionsDropDown.value == 2)
            Screen.SetResolution(1920, 1080, Screen.fullScreen);
        else if (resolutionsDropDown.value == 3)
            Screen.SetResolution(3840, 2160, Screen.fullScreen);
 
        PlayerPrefs.SetInt("resolutionNumber", resolutionsDropDown.value);
        optionIndex = resolutionsDropDown.value;    
    }

The default value is 1280x720 when I actually set it to start with 1920x1080.

You need to run this to make it stick.

PlayerPrefs.Save();

@rh_galaxy I added that, but it doesn’t save anyway.