I'm developing a a base site app for a multi-function site. So in this moment I'm developing only the responsive frame where the app will go. I want the page to have a header and 3 columns (2 lateral columns for ads and a middle column for the application). I want the lateral columns to appear only in resolutions above 850px. So I have the following code:

App.js:

<...imports, etc ...>
function App() {
    return (
        <Router>
            <Navbar />
            <div className='divAds'>
                <VerticalAd />
                <div className='divMiddle' >
                    <HorizontalAd />
                    <div className="App" >
                        <Switch>
                            <Route exact path="/" component={Main} />
                            <Route exact path="/about" component={About} />
                            <Redirect to="/" />
                        </Switch>
                    </div>
                </div>
                <VerticalAd />
            </div>
        </Router>
    )
}

and in VerticalAd component I have:

import React from 'react'
import VerticalSun from '../../img/sun-vert.jpg';
import { Image } from 'semantic-ui-react'
import './verticalAd.scss'

export const VerticalAd = () => (
    <div className='divVad'>
        <Image src={VerticalSun} rounded alt="Vertical Ad" />
        <Image src={VerticalSun} rounded alt="Vertical Ad" />
        <Image src={VerticalSun} rounded alt="Vertical Ad" />
    </div>

which created this page structure:

So I want the lateral columns to disapear in mobile screens so I had the following css to VerticalAd.scss:

.divVad {
    @media (min-width: 850px) {
        display: block;
    }

    @media (max-width: 849px) {
        display: none;
    }
    
    img {
        width: 10em;
        height: 50em;
    }
}

But the vertical columns won't disapear in lower resolutions. What am I doing wrong ?

I tried to move @media queries to App.scss but didn't work also.

I'm testing this using Chrome developer tools's responsive test.

Edit

The problem was developer tools. ASAI tested it by sizing the whole browser window it worked. Sorry. But anyway... @Samathingamajig answer's was useful and I have accept it. Sorry any inconvenience.