Code block which has a triple seat contact form is not resizing on mobile even with css added

Code block with triple seat contact form code is not resizing on mobile even with css added. appears ok in a browser, but not on mobile devices or squarespace mobile preview. 

https://www.skoposcatering.com/contact

added this css: 

/* resize code block mobile */
@media screen and (max-width:760px) {
#block-yui_3_17_2_1_1675451210488_9165 {
    width: 100% !important;
}
}

@Ziggy thank you!! using the code suggestion under "Mobile-Friendly Layout" worked!