icingaweb2/modules/monitoring/application/views/scripts/show/components/acknowledgement.phtml

<?php

/** @var \Icinga\Module\Monitoring\Object\MonitoredObject $object */

if (in_array((int) $object->state, array(0, 99))) {
    // Ignore this markup if the object is in a non-problem state or pending
    return;
}

if ($object->getType() === $object::TYPE_HOST) {
    $ackLink = $this->href(
        'monitoring/host/acknowledge-problem',
        array('host' => $object->getName())
    );
} else {
    $ackLink = $this->href(
        'monitoring/service/acknowledge-problem',
        array('host' => $object->getHost()->getName(), 'service' => $object->getName())
    );
}

if ($object->acknowledged): ?>
    <tr>
        <th><?= $this->translate('Acknowledged') ?></th>
        <td><?= $removeAckForm ?></td>
    </tr>
<?php else: ?>
    <tr>
        <th><?= $this->translate('Not acknowledged') ?></th>
        <td>
            <?php

            ?>
            <a href="<?= $ackLink ?>">
                <?= $this->icon('acknowledgement_petrol.png') ?> <?= $this->translate('Acknowledge') ?>
            </a>
        </td>
    </tr>
<?php endif ?>