Hiding HTML elements working on Desktop and Mobile browsers but not in the Android Studio WebView

As a preface, I am not very experienced with web development and am working on this for a university assignment.

My HTML Code

<!DOCTYPE html>c
<html lang="en">
    <head>
        <meta charset="UTF-8">
        <meta http-equiv="X-UA-Compatible" content="IE=edge">
        <meta name="viewport" content="width=device-width, initial-scale=1.0">
        <link rel="stylesheet" href="app.css">
    </head>
    <body>
        <div class="container">
            <div id="categoriesList" class="flex-center flex-column">
                <h1>Welcome to EduQuiz</h1>
                <a class= "btn" data-cat="20">Mythology</a>
                <a class= "btn" data-cat="23">History</a>
                <a class= "btn" data-cat="9">General Knowledge</a>
                <a class= "btn" data-cat="12">Music</a>
                <a class= "btn" data-cat="17">Science</a>
                <a class= "btn" data-cat="27">Animals</a>
                <a class= "btn" data-cat="22">Geography</a>
                <a class= "btn" data-cat="18">Information Technology</a>
            </div>
            <div id="difficulty" class="hidden flex-center flex-column">
                <a class= "btn" data-difficulty="easy"> Easy</a>
                <a class= "btn" data-difficulty="medium">Medium </a>
                <a class= "btn" data-difficulty="hard">Hard</a>
            </div>
        </div>
        <script src="categories.js"></script>
    </body>
</html>

My JavaScript code

    const category = Array.from(document.getElementsByClassName("btn"));
const allCats = document.getElementById('categoriesList');
const difficulties = document.getElementById('difficulty');

localStorage.clear();

category.forEach((cat => {
    cat.addEventListener('click', (e) => {
        console.log(e.target);
        allCats.classList.add('hidden');
        difficulties.style.left = "8rem";
        difficulties.classList.remove("hidden");

        if (cat.getAttribute("data-cat") != null) {
            localStorage.setItem("cat", cat.getAttribute("data-cat"));
            // const selectedCategory= localStorage.getItem("cat");
            //console.log(selectedCategory);
        }

        if (cat.getAttribute("data-difficulty") != null) {
            localStorage.setItem("difficulty", cat.getAttribute("data-difficulty"));
            buildString();
        }
    });

}));


function buildString() {
    const selectedCategory = localStorage.getItem("cat");
    console.log(selectedCategory);
    let selectedDifficulty = localStorage.getItem("difficulty");
    console.log(selectedDifficulty);

    let url = "https://opentdb.com/api.php?amount=10&category=";
    url += selectedCategory;
    url += "&difficulty=";
    url += selectedDifficulty;
    url += "&type=multiple";
    console.log(url);

    sessionStorage.setItem("diff", selectedDifficulty);
    sessionStorage.setItem("url", url);

    window.location = "game.html";
}

Problem:
On mobile browsers and desktop browsers the code works as intended. When a category is chosen, it hides the category buttons and shows the difficulty buttons. However, in the webview component of Android studio, when a category is chosen, nothing happens.

How should I fix this?