During Teams migration, users that are not added to Teams but there is nothing in the logs or otherwise indicating the user may not have been given permissions.
Log entry Severity: Info -"Provisioning of user skipped" but other users within the same migrations also have that message and do end up being added to the Teams when migration has completed. Is the Info message incorrect for the other users, or is it correct and something happened with the user '' with no proper warning or exception message in the logs?
Correct User mapping, Run the migration again.
++Please note++
Depending on how incorrect the mapping is you may need to rediscover to ensure everything is loaded correctly.