"Access level of user is not enough to complete copying" error message
The error message below is encountered when migrating a list from SharePoint On-Premises to SharePoint Online despite the migration account being a site collection administrator and an Office 365 tenant administrator:
The source site collection is set to read-only mode in SharePoint.
Open Central Administration.
Navigate to Application Management > Site Collections > Configure quotas and locks.
Select the source site collection, then set it to Not Locked.
Right-click on the source site collection and select Refresh.