I looked on your site on an iPhone emulator (375 x 667) and the CSS is indeed applied.
Can you please make sure you’ve cleared your browser cache, and look again?
On what device are you viewing the site and at what resolution? Which browser are you using please.
Lastly can you just confirm again you’re looking for the label to have a new line after it, before the input field? Just wanted to be absolutely sure on that in case I’ve misunderstood – as that is exactly what I’m seeing at my end.