I am also seeing this error now that it installed and the process did not have errors.
[E_ERROR] Uncaught TypeError: DateInterval::__construct() expects exactly 1 parameter, 2 given in /app/65y2iwmymaini/vendor/magento/module-reward/Model/ResourceModel/Reward/History/Collection.php:288
Stack trace:
#0 /app/65y2iwmymaini/vendor/magento/module-reward/Model/ResourceModel/Reward/History/Collection.php(288): DateInterval->__construct(‘P’, ‘15D’)
#1 /app/65y2iwmymaini/vendor/magento/module-reward/Cron/ScheduledBalanceExpireNotification.php(90): Magento\Reward\Model\ResourceModel\Reward\History\Collection->loadExpiredSoonPoints(‘1’, true)
#2 [internal function]: Magento\Reward\Cron\ScheduledBalanceExpireNotification->execute(Object(Magento\Cron\Model\Schedule\Interceptor))
#3 /app/65y2iwmymaini/vendor/magento/module-cron/Observer/ProcessCronQueueObserver.php(247): call_user_func_array(Array, Array)
#4 /app/65y2iwmymaini/vendor/magento/module-cron/Observer/ProcessCronQueueObserver.php(195): Magento\Cron\Observer\ProcessCronQueueObserver->_runJob(1472072460, 1472072462, Array, Object(Magento\Cron\Model\Schedule\I
Файл: /app/65y2iwmymaini/vendor/magento/module-reward/Model/ResourceModel/Reward/History/Collection.php`