Hide Blocks on mobile in Fluid Engine

Hey

I'm trying to hide 2 text blocks in the Mobile view using the following code which appears everywhere that I have looked for an answer:

// Hide this block on mobile //
@media only screen and (max-width: 767px) {
#BLOCK-ID {
   display: none;
 }
}

I'm using SS7.1 with Fluid Engine, and no matter what I do, the two blocks just won't go away.

Any ideas?

Can you share your website URL?