Hide in Desktop

Hi,
I’ve tried adding a custom css for it so it wouldn’t show on Desktop, at least that’s what I plan but it doesn’t seem to honor it. These are the css lines I’ve tried but failed:

@media only screen and (max-width: 768px) {
    #fpub-popup.trg-overlay.hide.small {
        display: block;
    }
}

the other one

@media only screen and (max-width: 768px) {
    #fpub-popup {
        display: block;
    }
}

I’m at loss since it won’t honor it I tried adding !important as well but to no avail. Any advice regarding this matter? Thanks!

https://wordpress.org/plugins/footer-pop-up-banner/