Support

You are looking at the wrong troubleshooting page. The page you are looking at is for Joomla 3. For Joomla 4 and later versions it's https://www.akeeba.com/documentation/admin-tools-joomla/atwafissues.html 

First, try deleting the .htaccess and .htpasswd files in the administrator directory.

I see that your restored sites are in a subdirectory. Is your original site in the root of the domain? If so, please note what I have written in https://www.akeeba.com/documentation/akeeba-backup-joomla/restoring-backups.html#general-guidelines 

Do not restore in a subdirectory of your main site. For example, if your site's root is in public_html do not restore to public_html/dev. The reason is that the .htaccess files, which tell Apache (your web server) how to server your site, cascade. That is, Apache will read all .htaccess files in all folders leading to the one hosting your site's index.php file. This will cause problems with the restored site which you will experience as 404, 403 and 500 error messages or blank pages. These have nothing to do with our software and / or the restoration. It's how your web server works. Use a subdomain instead.

Therefore, you'll have to use a subdomain AND make sure the subdomain's web root is outside your main site's web root.

During the restoration, the second to last page is Site Setup. On that page you can select a Super User account and enter a new password. Try that. Does that help you log in?