Restore My Esri administrative access after ArcGIS Online account deletion

Summary

If a Primary Maintenance Contact account is deleted from ArcGIS Online, the user loses administrative access to My Esri. A second My Esri administrator must manually restore their permissions.

Procedure

1. The second administrator must invite the deleted administrator to the My Esri organization. Grant all permissions. Refer to How to Administer Users on My Esri. 
2.  Before clicking the invitation link to join the organization, ensure the recipient (the deleted administrator) is fully signed out of any active sessions to avoid linking errors.
3. Accept the invitation sent to the deleted administrator's email account.