WordPress has 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, TaskHive.
First, visit your website and check for any visible issues. Next, visit the page where the error was caught (…/wp-admin/admin-ajax.php) and check for any visible issues.
Any suggestion on why this happened and how to prevent it in the future?