How toset plugin to send email to donor and admin when donation pending received

How to setup plugin to send email to donor and admin when donation pending received?

I did try use this:
https://github.com/Charitable/library/blob/master/emails/send-donation-notification-for-pending-offline-donations.php

in my child-theme function.php but it trigger error: when donor click Donate button, the page is not refreshing. there is only circle loading below the donate button, and nothing else happen..

Is there anyway I can modify the code in plugin, in order for me to achieve this as soon as possible?

https://wordpress.org/plugins/charitable/