1. Create a User by from Control Panel --> Users and Organizations
2. Add a Page and add a "Invite Members" Portlet to it.
3. Invite the new User to the page by clicking on "Invite members to this site" in portlet --> Click on the user then "Send Invitation".
4. Log in as the new User and check the "Notifications" and go to "Requests List". There you will see the invitation notification. Delete the notification from the 3 dots on the right side.
5. Log in back as Administrator and Invite the new User again.
6. Log in back as the new User.
Actual Result: User does not receive the invitation notification.
Expected Result: User should receive the invitation notification.
The reason for this behavior is that the membership request still remains in the im_memberrequest with a pending (0) status.
The MemberRequest* API does not support deleting an entry.
The solution is to disable deletion of the Notification Feed entry is actionable eg. not yet accepted or declined.