first of all, congratulations for this great theme
The Nirvana settings page does not work, I can only see the headers, but the content is not shown. The collapse/uncollapse effectis not working.
After several tests, it seems like an interference with the postsnippets plugin (https://wordpress.org/plugins/post-snippets/).
when post snippet is activated the settings page of Nirvana does not work. When I deactivate postSnippet the settings page of Nirvana works again.