ns-landscape does not work when I change my phone orientation to landscape mode

I am trying to change my font-size based on the orientation of the phone. Following this documentation: Documentation

Following is the code in my css file.

.item-title-heading {
    font-size: 18px;
    font-weight: 600;
    text-align: left;
    color: black;
}

.ns-landscape .item-title-heading{
    font-size: 14px;
}

In my HTML file I just, call the class like this:

<Label class="item-title-heading" text="Title Heading"></Label>

The issue that my code is always using .ns-landscape item-title-heading class and not using the item-title-heading ever.

I can't figure out what I am doing wrong.

Any kind of information would be helpful! Thanks in advance :)