I created a new sub-domain and installed a fresh copy of WordPress and the latest Pro and Pro child theme . When I attempt to launch Cornerstone or access the theme options, I get a 404.
The permalinks have already been set to post. The server has mod_rewrite on by default (dedicated server with Plesk Obsidian with NGINX/Apache) and the main domain and other sites on the same server running Pro have no issue. If I reset the permalinks to plain, the issue is resolved, but changing to any pretty links schema causes the 404.