Why does the file not change when editing on the server?

Question

WordPress

I have a hosted site on worpdress.
I want to make an animation on scroll.
So, I created a new js file, connected it to functions.php and wrote scripts. Interestingly, the animation worked.
But, I want to animate another element and for this you need to register id in index.php. So there is an id in the editor, but I open the site, but there is no id there.
Started changing index.php in several places, and those changes never showed up in the browser. For me, it's just magic.
What could be the reason?
After all, the animation in js has earned.
Thanks in advance.

Answer 1

And you know what was the problem, I just froze. The customer created a static page and uploaded the entire page code to the editor. I haven't seen this yet.