JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://e-timer.ru/js/etimer.js"></script>
      <h3>Flag documents</h3>
      <div class="ac-custom ac-radio">
        <input type="radio" name="radio11" id="radio11" value="Antigua and Barbuda">
        <label for="radio11">Antigua and Barbuda</label>
        <input type="radio" name="radio11" id="radio12" value="Bahamas">
        <label for="radio12">Bahamas</label>
        <input type="radio" name="radio11" id="radio13" value="Barbados">
        <label for="radio13">Barbados</label>
        <input type="radio" name="radio11" id="radio14" value="Belize">
        <label for="radio14">Belize</label>
        <input type="radio" name="radio11" id="radio15" value="Bermuda">
        <label for="radio15">Bermuda</label>
        <input type="radio" name="radio11" id="radio16" value="Cambodia">
        <label for="radio16">Cambodia</label>
        <input type="radio" name="radio11" id="radio17" value="Cayman Islands">
        <label for="radio17">Cayman Islands</label>
      </div>
      
      <div class="flagblock">
     Блок, который должен появится.
      </div>

CSS

.flagblock{
  display: none;
}