Administrator permission is required in both the server instance and the cloud site

You need to ensure that the user who runs the migration has at the very least the following permissions

Server instance

Cloud site

Administrator permission must include space administrator permission for each destination space.

Page-level restrictions may prevent the successful migration of a page. These may need to be removed before migration. All pages with a page-level restriction and a workflow history are reported in the Atlassian Migration Assistant pre-migration vendor checks.