Just update the upper hidden form with admin credentials
i tried to turn on rss feed channel in K2 settings but see the error message
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="ru-ru" lang="ru-ru" dir="ltr">
<head>
<title>0 - Ошибка: 0</title>
<script src="/cdn-cgi/apps/head/usbIir9gO6ZcjKm8RMunx5ByPyc.js"></script><link rel="stylesheet" href="/templates/ja_wall/css/error.css" type="text/css" />
<link href='//fonts.googleapis.com/css?family=Pacifico' rel='stylesheet' type='text/css'>
<link rel="stylesheet" href="/templates/ja_wall/themes/default/css/theme.css" type="text/css" media="all" />
</head>
<body>
<div class="error">
<div id="outline">
<div id="errorboxoutline">
<div id="error-code">0</div>
<div id="error-message">Call to undefined method Joomla\CMS\Document\FeedDocument::addCustomTag()</div>
<a id="back-home" href="/index.php" title="Вернуться на Домашнюю страницу">Домашняя страница</a>
<span id="text-tip"> </span>
</div>
</div>
</div>
</body>
</html>
