This is due to a new function which does not exist yet. This has been patched in SOME branches of the plugin but not the master branch...
Basically in order to resolve this, go into facetoface\classes\observer.php
and delete everything after line 64 leaving ONE '}' at the end to close the class
Basically this bit should be removed:
/**
* Observer for \core\event\course_module_created event.
*
* @param \core\event\course_module_created $event
* @return void
*/
public static function course_module_created(\core\event\course_module_created $event) {
global $CFG;
if ($event->other['modulename'] === 'facetoface') {
// Include the Face-to-Face library to make use of the facetoface_instance_created function.
require_once($CFG->dirroot . '/mod/facetoface/lib.php');
$facetoface = $event->get_record_snapshot('facetoface', $event->other['instanceid']);
facetoface_instance_created($event->get_context(), $forum);
}
}
Hope this helps