It looks like there might be a conflict with your Ground Hogg plugin. You could try temporarily disabling it to see if that fixes the issue. Either way, I would be happy to troubleshoot this for you if you don’t mind sending temporary access details for the site via our secure contact form.
I staged the site turned off all plugins except Microthemer and even switched to different themes (I use Reign child theme on production site).
Last version of WordPress.
The behaviour of MT did not change.
Still blank settings page, still no way to create selector.
But see for yourself. I created an admin user for you.