Hi,
I am using ZC 1.5.6c, PHP 7.3.15, and a template cloned from the responsive classic template.
https://www.proteawines.jp/shop/
I am trying to display in single column (as the topmost sidebox finally) but at the moment I cannot get it to actually display at all on a real mobile phone, although the display works on my desktop when emulating a mobile phone (Firefox, Google Chrome).
So if someone looks at my site on a PC, and shrinks the browser windows, or uses debugging and selects mobile display, the categories show. But not when using an Android smartphone for example.

I had to empty the hidden CSS directives for categories in responsive_default.css (also removed in responsive_tablet.css, there is no mention of hidden of categories in responsive_mobile.css).
I found the affecting stylesheets by debugging in the browser.

However, since the categories still do not display in single column on a physical mobile phone, I wonder if I can debug that reliably using the PC, or whether I need to try and debug on the actual phone.

I am suspecting maybe I need to add something to responsive_mobile.css, but am not sure where to continue with debugging.

Any tips much appreciated.

PS I aim to try to add the searchbox full-width near the top of the page also in mobile after this.