CalendR\Event\Exception\NoProviderFound:

[734918601]

        $factory = new \CalendR\Calendar;
        $month = $factory->getMonth(2020, 6);
        $events = $factory->getEvents($month);

CalendR\Event\Exception\NoProviderFound: in file /home/wwwroot/akstest.gewu.pro/tooth/vendor/yohang/calendr/src/CalendR/Event/Manager.php on line 68

[peter279k]

It means there is no event provider can be found on this event collection.

According to this event reference, it should define your own event provider.