Sticky menu won't work since latest update

Hello everyone!

I’m building my website locally using wampserver and apache.
I created a child-theme to change font colours and stuff like that and everything was working perfectly fine until yesterday’s update.

Now the style changes I made in the CSS file are not showing and the sticky menu is not sticky anymore so the menu options appear behind the content.

Have any of you had any problems like this one after an update? Can it be because I’m not working on-line?

Thank you very much for your help.

Here there’s a screen capture.