You’re getting the following error: “Access denied. You do not have permission to perform this action or access this resource” at the beginning of the migration from or to OneDrive or SharePoint.
or: Start() Error for : Fatal Exception on : — AccessDenied
Cause 1: during file migration
The migration account that is defined in the OneDrive connector doesn’t have the permissions to access the OneDrive of the user that you want to migrate.
Run the preprocessing task: it automatically provisions the OneDrive profile and sets the permissions.
The preprocessing task can be run from the user list.
You can also manually set the permissions.
Cause 2: during sites migration
The migration account that is defined in the SharePoint connector does not have enough permissions to access the SharePoint site.
1) Connect to SharePoint Central Administration (https://company-admin.sharepoint.com)
2) Select the site to access
3) Click on Owners -> Manage Administrators, then add you migration account to the site collection administrators
4) Wait until the change is complete and relaunch your migration