Website Error

Getting the following ERROR after update to  Observium Professional 23.9.13005:

Class "Mobile_Detect" not found in /opt/observium/html/includes/functions.inc.php:601

#0: (unknown function) called at [/opt/observium/html/includes/functions.inc.php:601]

596: *
597: * @return string Return type of browser (generic/mobile/tablet)
598: */
599: function get_browser_type($user_agent = NULL) {
600:
601: $detect = new Mobile_Detect;
602:
603: if (!is_null($user_agent)) {
604: // Set custom User-Agent
605: $detect->setUserAgent($user_agent);
{{606: }}}

#1: get_browser_type called at [/opt/observium/html/includes/functions.inc.php:564]

559: $ua_info['browser_full'] = $ua_info['browser'] . ' ' . preg_replace('/^([^\.](?:\.[^\.])?).*$/', '\1', $ua_info['version']);
560: //r($ua_info);
{{561: }}}
562:
563: // Detect Browser type & icon
564: $type = get_browser_type($user_agent);
565: $icon = get_browser_icon($type, $ua_info['platform']);
566:
567: $detect_browser = [
568: 'user_agent' => $user_agent,
569: 'type' => $type,

#2: detect_browser called at [/opt/observium/html/index.php:161]

156:
157: <?php
158:
159: if ($_SESSION['authenticated']) {
160: // Determine type of web browser.
161: $browser_type = detect_browser()['type'];
162: if ($browser_type === 'mobile' || $browser_type === 'tablet') {
163: session_set_var('touch', 'yes');
{{164: }}}
165: if ($vars['touch'] === "yes") {
166: session_set_var('touch', 'yes');