Problem Statement:
Admin users cannot edit the Manager email address associated with the external registration profile/group.

Role: Admin

Brief Description:
The email address associated with the external registration profile is frozen, so the Admin user cannot edit it.

Steps to resolve the issue:
Assigning the manager role to any other user within that External User Profile would remove the manager role from the existing Manager user.

Steps to be carried out by Agent:

• Login as Admin
• Go to Manage>>Users> External
• Click on the external Profile for which the email address needs to be updated.
• Select the intended user, then click on the action option to assign the Manager role to the user.
  

References Material:
https://helpx.adobe.com/learning-manager/administrators/feature-summary/add-users-user-groups.html