I see the error logs are showing several issues.
The Duplicate took a while to download and deploy locally; I did disable all plugins but Toolset during the Duplication.
I got some errors on login:
ERROR: Cookies are blocked due to unexpected output. For help, please see this documentation or try the support forums.
and
( ! ) Warning: Cannot modify header information - headers already sent by (output started at .../wp-includes/class-wp-hook.php:286) in .../wp-login.php on line 423
I was not able to log in, as upon sending in the login details, more errors happened:
( ! ) Warning: Parameter 2 to __search_by_title_only() expected to be a reference, value given in .../wp-includes/class-wp-hook.php on line 286
(Repeated many times)
I removed the theme, all modified htaccess, customization from said, removed all MU Plugins,
I hen could log in, and I downloaded a fresh set of Toolset form https://toolset.com/account/downloads/ and applied them to the duplicated site.
No issue was encountered during this process.
This problem is likely not due to Toolset, but the underlying issues on the site as shown above.
Something is interfering from the Theme or other Plugins, with WordPress Itself.
I recommend to deploy this site locally and solve those issues one by one, so to later deploy them online.
That will likely solve future issues as those errors will not stop other plugins from executing anymore.
Later on the duplicate I also re-activated theme, and plugins.
I got again errors:
( ! ) Fatal error: Uncaught Error: Call to undefined function mysql_error() in .../plugins/revslider/inc_php/framework/db.class.php on line 29
Those are not related to Toolset.