Issue with review reminder plugin

Hello!

Hope you doing well. I’m facing strange issue on my website. I’ve set up everything correctly. I have set 2 days for the review reminder but emails are not sent automatically. Also, when I try to send the reminder manually then I get this error.
https://tinyurl.com/yxe7ba33

Also, I immediately receive this email in my inbox from the WordPress.

Since WordPress 5.2 there is a built-in feature that detects when a plugin or theme causes a fatal error on your site, and notifies you with this automated email.

In this case, WordPress caught an error with your theme, Online24/7 Child theme.

First, visit your website (https://aroundtheclockgifts.com/) and check for any visible issues. Next, visit the page where the error was caught (https://aroundtheclockgifts.com/wp-admin/edit.php?s=