Just to add, Also You could possibly have wordfence installed but not active, activate it, the issue is that the migration is suffering from a 403 error somewhere. WordFence was my issue, when I activated the plugin everything went through.
Anyone still struggling keep going back versions, VERSION 6.77 worked for me.
Found at
https://pluginarchive.com/wordpress/all-in-one-wp-migration/v/6-77/6-69
