Scheduling Error?

After scheduling a giveaway, the post (with the shortcode to the giveaway) fails to include the giveaway design/details but instead displays < 0 hours 0 minutes 0 seconds > yet the direct URL to the giveaway *does* display the correct, remaining time, background image, etc. ~ In other words, the shortcode did not embed the giveaway, and the schedule did not publish on time.

At the beginning of the post, I git this error:

Warning: DateTime::setTimestamp() expects parameter 1 to be long, string given in /home/XXXXXXX/public_html/wp-content/plugins/giveasap/includes/class-schedule.php on line 183

I tried to re-schedule the giveaway with a later time (15 minutes) but it did not work ~ so I had to re-write the post (and the giveaway mechanism via this plugin) and manually administer the contest on Facebook. (And once the shot code was removed, of course the above error no longer displayed.)

I can try again for a future giveaway, but how?

Here are some URLs to review:
https://www.eastcobber.com/enter-to-win-a-50-gift-certificate-to-snowville-shavery/
https://www.eastcobber.com/giveaway/50-gift-certificate-snowville-shavery/