XF 2.1 Can't get RSS after lastest version upgrade

[Hizen]

I recently upgraded my forum (https://forum.blackout-ro.net) to the latest version (from the version before it).

We have another site (https://cp.blackout-ro.net) which fetches the RSS from https://forum.blackout-ro.net/forums/announcements/index.rss, however, the code on that other site stopped working. It's strange because we can get fetch the RSS fine from our main website (https://blackout-ro.net).

This is the function that was being used. It worked perfectly until the upgrade and it hasn't been changed. The value $channels no longer returns anything (e.g. count($channels) would equal 0).

I know this message is a long shot since there is technically nothing wrong with XenForo, but I'm stuck. I've tried everything. Hoping someone can help me out.

function RSS_Display($url, $feed_items)
{
    $feed_file = FLUX_DATA_DIR.'/tmp/Feed_.php';
    if (file_exists($feed_file) && time_check('+5 minutes', $feed_file)) {
        return unserialize(file_get_contents($feed_file, null, null, 28));
    } else {
        global $RSS_Content;
        foreach ($url as $cat => $url_) {
            foreach($url_['links'] as $url1) {
                $doc = new DOMDocument();
                $url1 = "https://forum.blackout-ro.net/forums/announcements/index.rss?&order=post_date";
                $doc->load(trim($url1));

                $titles = [];

                $channels = $doc->getElementsByTagName("channel");

                foreach ($channels as $channel) {
                    $items_ = $channel->getElementsByTagName('item');
                    foreach($items_ as $item1) {
                        $tnl = $item1->getElementsByTagName("title");
                        $tnl = $tnl->item(0);
                        $title = $tnl->firstChild->textContent;
                        $titles[] = $title;
                    }
                }
            }
        }
        return serialize_cache($feed_file, array_slice($RSS_Content, 0, $feed_items));
    }
}