Scroll to top button does not show in mobile view

Hello everyone, I am Kris from Hong Kong. As a digital marketer with no-code, I was required by my employer to build an event site.

As I have some experience to build my own website before, so everything go fines at all, until the scroll to top button does not show up in mobile view.

I am using Kadence theme, and enabled scroll to top function, also clicked mobile visibility, it could be shown in preview, but if we use iPhone or android, the button does not show up in production.

I have searched in google and add some custom css script, it does not work too. As we need to launch the website to public before 27 OCT, can anyone help me? thanks a lot.