Exchange Impersonation error. Unable to open user mailbox due to impersonation error. Please make sure impersonation is set properly. (11021)
Log into to ECP e.g. https://admin.exchange.microsoft.com/#/adminRoles
Select the Permissions menu, then Admin Roles
Create a new role by clicking on the + sign
Give it a name e.g. GSuiteMigration
Click on the + under roles and add the ApplicationImpersonation & ViewOnly-Configuration
Click the + sign under members and add the admin that requires the impersonation role
Save and rerun the migration steps