Quota Warning App not Sending Notification to Users Email Address or Mail Box

Hey I am running Nextcloud 21.02 version in on-premises based on centos 7 and merge AD with Nextcloud Server for user authentication. So far everything running well.

However I would like to send mail to users regarding their quota usage. I have found the quota warning app. I have installed the app and configure threshold value to send notification and mail.

I have configured the email server as well for sending notification and it’s working fine.

But Quota warning app is not sending email to users regarding their quota usage it’s only send notification to users web portal. How can I solve this problem. Anyone have faced similar problem and how you solved that?
Here is the installation details:

PHP Version : 7.4.16

Web server: Apache 2.4.6
Type: mysql
Version: 10.5.9