Markdown crash

google-calendar-events plugin version 3.1.36. Crashes for [description markdown=”yes”] saying ‘ParseDown’ not found

Tidied up log file excerpt:

PHP Fatal error: Uncaught Error: Class ‘Parsedown’ not found in wp-content/plugins/google-calendar-events/includes/events/event-builder.php:673, referer: https://…/wp-admin/post.php?post=80&action=edit
Stack trace:, referer: https://…/wp-admin/post.php?post=80&action=edit
#0 wp-content/plugins/google-calendar-events/includes/events/event-builder.php(284): SimpleCalendar\\Events\\Event_Builder->get_description(‘[Join YouTube L…’, Array), referer: https://…/wp-admin/post.php?post=80&action=edit
#1 [internal function]: SimpleCalendar\\Events\\Event_Builder->process_event_content(Array), referer: https://…/wp-admin/post.php?post=80&action=edit
#2 wp-content/plugins/google-calendar-events/includes/events/event-builder.php(238): preg_replace_callback(‘/\\\\[(\\\\[?)(title|…’, Array, ‘<p>[tit…’), referer: https://…/wp-admin/post.php?post=80&action=edit
#3 wp-content/plugins/google-calendar-events/includes/abstracts/calendar.php(753): SimpleCalendar\\Events\\Event_Builder->parse_event_template_tags(‘<p>[tit…’), referer: https://…/wp-admin/post.php?post=80&action=edit
#4 wp-content/plugins/simple-calendar-fullcalendar/includes/calendars/views/fullcalendar-grid. in /home/jacobvc/…/wp-content/plugins/google-calendar-events/includes/events/event-builder.php on line 673, referer: https://…/wp-admin/post.php?post=80&action=edit