It's possible that you initially signed up with Apple and opted to 'hide my email' when prompted to share your email address. In such cases, Apple generates a 'private relay' email address for you. (it will appear similar to 'abcd1234@privaterelay.appleid.com')
On your iPhone or iPad:
Open your Device's settings
Click on your Name - Apple ID, iCloud, Media and Purchases
Tap on 'Password and Security '
Choose 'Sign in with Apple' or 'Apps Using Apple ID'
Select the Hallow app.
You will see your Relay Email under "Hide My Email" - "This App Received"
On your desktop or laptop:
Sign in to appleid.apple.com
Go to the 'Sign in & Security' tab
Click 'Sign in with Apple'
Click 'Hallow'
You will see your Relay Email under 'Hide My Email'
I’ve posted a screenshot below of how it would look like on your iPhone or iPad:
We’re always here to help when you need it. You can reach out through this purple chat window on the bottom-right corner or e-mail us at support@hallow.app
God bless 🕊️