Site not loading in Firefox and Admin not accessible in any other browser

My website will not display in Firefox.
The site WILL display in Chrome, but the Admin page will not (http://hardcheapknock.com/wp-admin/). The console says "Failed to load resource: the server responded with a status of 500 (Internal Server Error)"

I did receive an email that the site was upgraded to WordPress 4.9.8 yesterday.