Media Queries Not Working #2

Issue: Media queries are not working :(

During study group, our goal is to apply the responsive design so we used media queries.
But it seems that no matter what media query we apply, it doesn't work. After debugging, we found out that we need to add <meta name="viewport" content="width=device-width, initial-scale=1.0"> in order for media queries to work.

But the main question is, Is it necessary to add <meta name="viewport" content="width=device-width, initial-scale=1.0"> for the media queries to work?

In our case, we need to add the meta viewport tag while on others, they've managed to use media queries without using the meta viewport tag.

Thanks.