Group Member not getting email notification from On-Call Schedule subscription

Group Member is trying to click send subscription button from On-Call Schedule Calendar, but he is not receiving any email notification, other members of the group are receiving the notification.Group members are having "rota_admin" role.

The group members who are part of Shift tries to click the send subscription button from On-Call Calendar, other than the person who clicked remaining persons were able to receive the email notifications.  

This is expected behaviour in the OOB (out of box) across all instances.