Custom code suddenly not working only on one site?

I have a lot of custom code on my site that hides certain sections on desktop/mobile. It has suddenly stopped working on my personal site, but I checked my clients site (that are on my account) and the exact codes are still working? This is an example of the code, if it helps. Really not sure what the issue is if the exact thing is working on other sites but it's really frustrating!

// Hide this block on desktop //
@media only screen and (min-width: 750px) {

#block-yui_3_17_2_1_1676664519374_26359 {

   display: none;

 }

}

Hi, @juliegarcia if probably isn't the exact same code, because the CSS selector would be different. Please can you share the website that you are having issue with, so I can check?