Prestashop voucher box doesn't toggle and voucher codes don't work

Question

Suddenly the voucher box in the cart (checkout) is not being toggled on and off so I can't add any promo code. I have meddled with its CSS and managed to make it always show, but none of my cart rules work. In the console there is no error.

I have checked and all of my cart rules are correct. The cart rules appear also in my db and are active. PS_CART_RULE_FEATURE_ACTIVE is already 1. I don't have a PayPal module. I didn't install any modules nor updated anything and yet this issue arose.

I use PrestaShop 1.7.8.8. PHP is 7.4.3.3

Below is the code of cart-voucher.tpl

{**
* 2007-2020 PrestaShop
*
* NOTICE OF LICENSE
*
* This source file is subject to the Academic Free License 3.0 (AFL-3.0)
* that is bundled with this package in the file LICENSE.txt.
* It is also available through the world-wide-web at this URL:
* https://opensource.org/licenses/AFL-3.0
* If you did not receive a copy of the license and are unable to
* obtain it through the world-wide-web, please send an email
* to [email protected] so we can send you a copy immediately.
*
* DISCLAIMER
*
* Do not edit or add to this file if you wish to upgrade PrestaShop to newer
* versions in the future. If you wish to customize PrestaShop for your
* needs please refer to http://www.prestashop.com for more information.
*
* @author PrestaShop SA <[email protected]>
    * @copyright 2007-2020 PrestaShop SA
    * @license https://opensource.org/licenses/AFL-3.0 Academic Free License 3.0 (AFL-3.0)
    * International Registered Trademark & Property of PrestaShop SA
    *}
    {if $cart.vouchers.allowed}
        {block name='cart_voucher'}
            <div class="block-promo">
                <div class="cart-voucher">
                    {if $cart.vouchers.added}
                        {block name='cart_voucher_list'}
                            <ul class="promo-name card-block">
                                {foreach from=$cart.vouchers.added item=voucher}
                                    <li class="cart-summary-line">
                                        <span class="label">{$voucher.name}</span>
                                        <a href="{$voucher.delete_url}" data-link-action="remove-voucher"><i class="material-icons">&#xE872;</i></a>
                                        <div class="float-xs-right">
                                            {$voucher.reduction_formatted}
                                        </div>
                                    </li>
                                {/foreach}
                            </ul>
                        {/block}
                    {/if}

            <p>
                <a class="collapse-button promo-code-button" data-toggle="collapse" href="#promo-code" aria-expanded="false" aria-controls="promo-code">
                    {l s='Have a promo code?' d='Shop.Theme.Checkout'}
                </a>
            </p>

            <div class="promo-code collapse{if $cart.discounts|count > 0} in{/if}" id="promo-code">
                {block name='cart_voucher_form'}
                <form action="{$urls.pages.cart}" data-link-action="add-voucher" method="post">
                    <input type="hidden" name="token" value="{$static_token}">
                    <input type="hidden" name="addDiscount" value="1">
                    <input class="promo-input" type="text" name="discount_name" placeholder="{l s='Promo code' d='Shop.Theme.Checkout'}">
                    <button type="submit" class="btn btn-primary"><span>{l s='Add' d='Shop.Theme.Actions'}</span></button>
                </form>
                {/block}

                {block name='cart_voucher_notifications'}
                <div class="alert alert-danger js-error" role="alert">
                    <i class="material-icons">&#xE001;</i><span class="ml-1 js-error-text"></span>
                </div>
                {/block}
            </div>

            {if $cart.discounts|count > 0}
            <p class="block-promo promo-highlighted">
                {l s='Take advantage of our exclusive offers:' d='Shop.Theme.Actions'}
            </p>
            <ul class="js-discount card-block promo-discounts">
                {foreach from=$cart.discounts item=discount}
                <li class="cart-summary-line">
                    <span class="label"><span class="code">{$discount.code}</span> - {$discount.name}</span>
                </li>
                {/foreach}
            </ul>
            {/if}
        </div>
    </div>
    {/block}
    {/if}

I have checked cart rules, I have checked the db and ps_cart_rule_feature_active and also all modules. I think the display of the box is an issue that derives from the fact that none of the code works, since probably (I can't debug) since

 <div class="promo-code collapse{if $cart.discounts|count > 0} in{/if}" id="promo-code">

The condition in this div most likely evaluates to false so the in class isn't applied.