Snippet not working

I have installed this plugin to be able to add click-open popups in my WooCommerce storefront website, but popups don’t seem to be working. Below is my snippet

add_filter( 'woocommerce_product_tabs', 'woo_shipping_returns_product_tab' );

function woo_shipping_returns_product_tab( $tabs ) {
  
  $tabs['ship_tab'] = array(
	'title' 	=> __( 'Shipping & Returns', 'woocommerce' ),
	'priority' 	=> 50,
	'callback' 	=> 'woo_shipping_returns_product_tab_content'
  );
  
  return $tabs;

}

function woo_shipping_returns_product_tab_content() {
  echo '<p class="popup" onclick="myFunction()">Pay on delivery<span class="popuptext" id="myPopup">Cash, Card, and Mobile Money</span></p>';
	
}

add_action( 'wp_head', function () { ?>
<script>

		function myFunction() {
		  var popup = document.getElementById("myPopup");
		  popup.classList.toggle("show");
		}

</script>
<?php } );

And my CSS in WordPress customizer looks like this

/* The actual popup (appears on top) */
.popup .popuptext {
  visibility: hidden;
  width: 160px;
  background-color: #555;
  color: #fff;
  text-align: center;
  border-radius: 6px;
  padding: 8px 0;
  position: absolute;
  z-index: 1;
  bottom: 125%;
  left: 50%;
  margin-left: -80px;
}

/* Popup arrow */
.popup .popuptext::after {
  content: "";
  position: absolute;
  top: 100%;
  left: 50%;
  margin-left: -5px;
  border-width: 5px;
  border-style: solid;
  border-color: #555 transparent transparent transparent;
}

/* Toggle this class when clicking on the popup container (hide and show the popup) */
.popup .show {
  visibility: visible;
  -webkit-animation: fadeIn 1s;
  animation: fadeIn 1s
}

/* Add animation (fade in the popup) */
@-webkit-keyframes fadeIn {
  from {opacity: 0;}
  to {opacity: 1;}
}

@keyframes fadeIn {
  from {opacity: 0;}
  to {opacity:1 ;}
}