Chances are this is not the first website you’ve come to after breaking SSL on your Nginx box, but I promise it will be the last. The problem is actually a very simple one, and the Nginx error log tells you verbatim what is wrong with the config, although nginx -t will yield success. Nginx reads and runs the sites in alphabetical order, therefore this issue can be fixed by finding and fixing the site config which is listening on port 443 and using ssl without any ssl certificate declarations which is causing your site further down the alphabetical line to fail HTTPS. In my case it was a Nginx site config called stub_status.conf causing SSL to fail in sysinfo.io.conf even though I did have SSL correctly setup.
How To Create Temporary and Permanent Redirects with Apache and Nginx