Changing css class with classList.add not working

I wanna add a class that makes a button looks disabled with calssList.add, I’m having hard time snice yesterday with this since i can’t see any difference on the button, even if i see in the inspector that the button is having the css class that i wanna add, it doesn’t make any changes.

                    alert("You can't have more than two articles in this layout");
                    saveButton.disabled = true;
                    saveButton.classList.add("fl-button-disabled"); ```


//css

 .fl-settings-save.fl-button.fl-button-large.fl-button-disabled{
    pointer-events: none;
    color: #666666;
    background-color: gray;
    border: 1px solid gray;
}