I have tried to add a group email for a custom email address for the release pipeline but still no email, is this a vsts bug or I am doing something wrong
the release pipeline name and stage name are correct , I've verified it
Can you try configuring the Delivery Setting.
The following delivery settings are available for a group or team:
Deliver to email address: notifications are delivered to a specific email address.
Deliver to individual members: notifications are delivered to each member of the group or team. This is usually the default option. See the section on "team expansion" below for more details on how this option works.
Do not deliver: notifications are not delivered by default.
From this you could try the Deliver to email address