For some users in our application, the email field returns NULL even if the user has granted the email access to the app. When we check the scope parameter and the validity
All you need to know:
1) Link 1
Some possible reasons:
No Email address on account
No confirmed email address on account
No verified email address on account
User entered a security checkpoint which required them to reconfirm their email address and they have not yet done so
Users's email address is unreachable
You also need the 'email' extended permission, even for users who have a valid, confirmed, reachable email address on file.
2) Link 2
Note, even if you request the email permission it is not guaranteed you will get an email address. For example, if someone signed up for Facebook with a phone number instead of an email address, the email field may be empty.